update php samples

samples/client/echo_api/php-nextgen/docs/Model/DefaultValue.md

@@ -4,10 +4,10 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**array_string_enum_ref_default** | [**\OpenAPI\Client\Model\StringEnumRef[]**](StringEnumRef.md) |  | [optional]
-**array_string_enum_default** | **string[]** |  | [optional]
-**array_string_default** | **string[]** |  | [optional]
-**array_integer_default** | **int[]** |  | [optional]
+**array_string_enum_ref_default** | [**\OpenAPI\Client\Model\StringEnumRef[]**](StringEnumRef.md) |  | [optional] [default to [["success","failure"]]]
+**array_string_enum_default** | **string[]** |  | [optional] [default to [["success","failure"]]]
+**array_string_default** | **string[]** |  | [optional] [default to [["failure","skipped"]]]
+**array_integer_default** | **int[]** |  | [optional] [default to [[1,3]]]
 **array_string** | **string[]** |  | [optional]
 **array_string_nullable** | **string[]** |  | [optional]
 **array_string_extension_nullable** | **string[]** |  | [optional]

samples/client/echo_api/php-nextgen/docs/Model/Query.md

@@ -5,6 +5,6 @@
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
 **id** | **int** | Query | [optional]
-**outcomes** | **string[]** |  | [optional]
+**outcomes** | **string[]** |  | [optional] [default to [["SUCCESS","FAILURE"]]]
 
 [[Back to Model list]](../../README.md#models) [[Back to API list]](../../README.md#endpoints) [[Back to README]](../../README.md)

samples/client/echo_api/php-nextgen/src/Api/AuthApi.php

@@ -28,6 +28,7 @@
 
 namespace OpenAPI\Client\Api;
 
+use InvalidArgumentException;
 use GuzzleHttp\Client;
 use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\ConnectException;
@@ -35,6 +36,7 @@ use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\RequestOptions;
+use GuzzleHttp\Promise\PromiseInterface;
 use OpenAPI\Client\ApiException;
 use OpenAPI\Client\Configuration;
 use OpenAPI\Client\HeaderSelector;
@@ -53,22 +55,22 @@ class AuthApi
     /**
      * @var ClientInterface
      */
-    protected $client;
+    protected ClientInterface $client;
 
     /**
      * @var Configuration
      */
-    protected $config;
+    protected Configuration $config;
 
     /**
      * @var HeaderSelector
      */
-    protected $headerSelector;
+    protected HeaderSelector $headerSelector;
 
     /**
      * @var int Host index
      */
-    protected $hostIndex;
+    protected int $hostIndex;
 
     /** @var string[] $contentTypes **/
     public const contentTypes = [
@@ -78,16 +80,16 @@ class AuthApi
     ];
 
     /**
-     * @param ClientInterface $client
-     * @param Configuration   $config
-     * @param HeaderSelector  $selector
+     * @param ClientInterface|null $client
+     * @param Configuration|null   $config
+     * @param HeaderSelector|null  $selector
      * @param int                  $hostIndex (Optional) host index to select the list of hosts if defined in the OpenAPI spec
      */
     public function __construct(
         ClientInterface $client = null,
         Configuration $config = null,
         HeaderSelector $selector = null,
-        $hostIndex = 0
+        int $hostIndex = 0
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -100,7 +102,7 @@ class AuthApi
      *
      * @param int $hostIndex Host index (required)
      */
-    public function setHostIndex($hostIndex): void
+    public function setHostIndex(int $hostIndex): void
     {
         $this->hostIndex = $hostIndex;
     }
@@ -110,7 +112,7 @@ class AuthApi
      *
      * @return int Host index
      */
-    public function getHostIndex()
+    public function getHostIndex(): int
     {
         return $this->hostIndex;
     }
@@ -118,7 +120,7 @@ class AuthApi
     /**
      * @return Configuration
      */
-    public function getConfig()
+    public function getConfig(): Configuration
     {
         return $this->config;
     }
@@ -130,11 +132,13 @@ class AuthApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testAuthHttpBasic'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testAuthHttpBasic(string $contentType = self::contentTypes['testAuthHttpBasic'][0])
+    public function testAuthHttpBasic(
+        string $contentType = self::contentTypes['testAuthHttpBasic'][0]
+    ): string
     {
         list($response) = $this->testAuthHttpBasicWithHttpInfo($contentType);
         return $response;
@@ -147,11 +151,13 @@ class AuthApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testAuthHttpBasic'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testAuthHttpBasicWithHttpInfo(string $contentType = self::contentTypes['testAuthHttpBasic'][0])
+    public function testAuthHttpBasicWithHttpInfo(
+        string $contentType = self::contentTypes['testAuthHttpBasic'][0]
+    ): array
     {
         $request = $this->testAuthHttpBasicRequest($contentType);
 
@@ -246,10 +252,12 @@ class AuthApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testAuthHttpBasic'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testAuthHttpBasicAsync(string $contentType = self::contentTypes['testAuthHttpBasic'][0])
+    public function testAuthHttpBasicAsync(
+        string $contentType = self::contentTypes['testAuthHttpBasic'][0]
+    ): PromiseInterface
     {
         return $this->testAuthHttpBasicAsyncWithHttpInfo($contentType)
             ->then(
@@ -266,10 +274,12 @@ class AuthApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testAuthHttpBasic'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testAuthHttpBasicAsyncWithHttpInfo(string $contentType = self::contentTypes['testAuthHttpBasic'][0])
+    public function testAuthHttpBasicAsyncWithHttpInfo(
+        string $contentType = self::contentTypes['testAuthHttpBasic'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testAuthHttpBasicRequest($contentType);
@@ -315,10 +325,12 @@ class AuthApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testAuthHttpBasic'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testAuthHttpBasicRequest(string $contentType = self::contentTypes['testAuthHttpBasic'][0])
+    public function testAuthHttpBasicRequest(
+        string $contentType = self::contentTypes['testAuthHttpBasic'][0]
+    ): Request
     {
 
 
@@ -396,7 +408,7 @@ class AuthApi
      * @throws \RuntimeException on file opening failure
      * @return array of http client options
      */
-    protected function createHttpClientOption()
+    protected function createHttpClientOption(): array
     {
         $options = [];
         if ($this->config->getDebug()) {

samples/client/echo_api/php-nextgen/src/Api/BodyApi.php

@@ -28,6 +28,7 @@
 
 namespace OpenAPI\Client\Api;
 
+use InvalidArgumentException;
 use GuzzleHttp\Client;
 use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\ConnectException;
@@ -35,6 +36,7 @@ use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\RequestOptions;
+use GuzzleHttp\Promise\PromiseInterface;
 use OpenAPI\Client\ApiException;
 use OpenAPI\Client\Configuration;
 use OpenAPI\Client\HeaderSelector;
@@ -53,22 +55,22 @@ class BodyApi
     /**
      * @var ClientInterface
      */
-    protected $client;
+    protected ClientInterface $client;
 
     /**
      * @var Configuration
      */
-    protected $config;
+    protected Configuration $config;
 
     /**
      * @var HeaderSelector
      */
-    protected $headerSelector;
+    protected HeaderSelector $headerSelector;
 
     /**
      * @var int Host index
      */
-    protected $hostIndex;
+    protected int $hostIndex;
 
     /** @var string[] $contentTypes **/
     public const contentTypes = [
@@ -96,16 +98,16 @@ class BodyApi
     ];
 
     /**
-     * @param ClientInterface $client
-     * @param Configuration   $config
-     * @param HeaderSelector  $selector
+     * @param ClientInterface|null $client
+     * @param Configuration|null   $config
+     * @param HeaderSelector|null  $selector
      * @param int                  $hostIndex (Optional) host index to select the list of hosts if defined in the OpenAPI spec
      */
     public function __construct(
         ClientInterface $client = null,
         Configuration $config = null,
         HeaderSelector $selector = null,
-        $hostIndex = 0
+        int $hostIndex = 0
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -118,7 +120,7 @@ class BodyApi
      *
      * @param int $hostIndex Host index (required)
      */
-    public function setHostIndex($hostIndex): void
+    public function setHostIndex(int $hostIndex): void
     {
         $this->hostIndex = $hostIndex;
     }
@@ -128,7 +130,7 @@ class BodyApi
      *
      * @return int Host index
      */
-    public function getHostIndex()
+    public function getHostIndex(): int
     {
         return $this->hostIndex;
     }
@@ -136,7 +138,7 @@ class BodyApi
     /**
      * @return Configuration
      */
-    public function getConfig()
+    public function getConfig(): Configuration
     {
         return $this->config;
     }
@@ -148,11 +150,13 @@ class BodyApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBinaryGif'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return \SplFileObject
      */
-    public function testBinaryGif(string $contentType = self::contentTypes['testBinaryGif'][0])
+    public function testBinaryGif(
+        string $contentType = self::contentTypes['testBinaryGif'][0]
+    ): \SplFileObject
     {
         list($response) = $this->testBinaryGifWithHttpInfo($contentType);
         return $response;
@@ -165,11 +169,13 @@ class BodyApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBinaryGif'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of \SplFileObject, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testBinaryGifWithHttpInfo(string $contentType = self::contentTypes['testBinaryGif'][0])
+    public function testBinaryGifWithHttpInfo(
+        string $contentType = self::contentTypes['testBinaryGif'][0]
+    ): array
     {
         $request = $this->testBinaryGifRequest($contentType);
 
@@ -264,10 +270,12 @@ class BodyApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBinaryGif'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testBinaryGifAsync(string $contentType = self::contentTypes['testBinaryGif'][0])
+    public function testBinaryGifAsync(
+        string $contentType = self::contentTypes['testBinaryGif'][0]
+    ): PromiseInterface
     {
         return $this->testBinaryGifAsyncWithHttpInfo($contentType)
             ->then(
@@ -284,10 +292,12 @@ class BodyApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBinaryGif'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testBinaryGifAsyncWithHttpInfo(string $contentType = self::contentTypes['testBinaryGif'][0])
+    public function testBinaryGifAsyncWithHttpInfo(
+        string $contentType = self::contentTypes['testBinaryGif'][0]
+    ): PromiseInterface
     {
         $returnType = '\SplFileObject';
         $request = $this->testBinaryGifRequest($contentType);
@@ -333,10 +343,12 @@ class BodyApi
      *
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBinaryGif'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testBinaryGifRequest(string $contentType = self::contentTypes['testBinaryGif'][0])
+    public function testBinaryGifRequest(
+        string $contentType = self::contentTypes['testBinaryGif'][0]
+    ): Request
     {
 
 
@@ -409,14 +421,17 @@ class BodyApi
      *
      * Test body parameter(s)
      *
-     * @param  \SplFileObject $body body (optional)
+     * @param  \SplFileObject|null $body body (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyApplicationOctetstreamBinary'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testBodyApplicationOctetstreamBinary($body = null, string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0])
+    public function testBodyApplicationOctetstreamBinary(
+        ?\SplFileObject $body = null,
+        string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0]
+    ): string
     {
         list($response) = $this->testBodyApplicationOctetstreamBinaryWithHttpInfo($body, $contentType);
         return $response;
@@ -427,14 +442,17 @@ class BodyApi
      *
      * Test body parameter(s)
      *
-     * @param  \SplFileObject $body (optional)
+     * @param  \SplFileObject|null $body (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyApplicationOctetstreamBinary'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testBodyApplicationOctetstreamBinaryWithHttpInfo($body = null, string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0])
+    public function testBodyApplicationOctetstreamBinaryWithHttpInfo(
+        ?\SplFileObject $body = null,
+        string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0]
+    ): array
     {
         $request = $this->testBodyApplicationOctetstreamBinaryRequest($body, $contentType);
 
@@ -527,13 +545,16 @@ class BodyApi
      *
      * Test body parameter(s)
      *
-     * @param  \SplFileObject $body (optional)
+     * @param  \SplFileObject|null $body (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyApplicationOctetstreamBinary'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testBodyApplicationOctetstreamBinaryAsync($body = null, string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0])
+    public function testBodyApplicationOctetstreamBinaryAsync(
+        ?\SplFileObject $body = null,
+        string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0]
+    ): PromiseInterface
     {
         return $this->testBodyApplicationOctetstreamBinaryAsyncWithHttpInfo($body, $contentType)
             ->then(
@@ -548,13 +569,16 @@ class BodyApi
      *
      * Test body parameter(s)
      *
-     * @param  \SplFileObject $body (optional)
+     * @param  \SplFileObject|null $body (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyApplicationOctetstreamBinary'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testBodyApplicationOctetstreamBinaryAsyncWithHttpInfo($body = null, string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0])
+    public function testBodyApplicationOctetstreamBinaryAsyncWithHttpInfo(
+        $body = null,
+        string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testBodyApplicationOctetstreamBinaryRequest($body, $contentType);
@@ -598,13 +622,16 @@ class BodyApi
     /**
      * Create request for operation 'testBodyApplicationOctetstreamBinary'
      *
-     * @param  \SplFileObject $body (optional)
+     * @param  \SplFileObject|null $body (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyApplicationOctetstreamBinary'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testBodyApplicationOctetstreamBinaryRequest($body = null, string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0])
+    public function testBodyApplicationOctetstreamBinaryRequest(
+        $body = null,
+        string $contentType = self::contentTypes['testBodyApplicationOctetstreamBinary'][0]
+    ): Request
     {
 
 
@@ -688,11 +715,14 @@ class BodyApi
      * @param  \SplFileObject[] $files files (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyMultipartFormdataArrayOfBinary'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testBodyMultipartFormdataArrayOfBinary($files, string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0])
+    public function testBodyMultipartFormdataArrayOfBinary(
+        array $files,
+        string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0]
+    ): string
     {
         list($response) = $this->testBodyMultipartFormdataArrayOfBinaryWithHttpInfo($files, $contentType);
         return $response;
@@ -706,11 +736,14 @@ class BodyApi
      * @param  \SplFileObject[] $files (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyMultipartFormdataArrayOfBinary'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testBodyMultipartFormdataArrayOfBinaryWithHttpInfo($files, string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0])
+    public function testBodyMultipartFormdataArrayOfBinaryWithHttpInfo(
+        array $files,
+        string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0]
+    ): array
     {
         $request = $this->testBodyMultipartFormdataArrayOfBinaryRequest($files, $contentType);
 
@@ -806,10 +839,13 @@ class BodyApi
      * @param  \SplFileObject[] $files (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyMultipartFormdataArrayOfBinary'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testBodyMultipartFormdataArrayOfBinaryAsync($files, string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0])
+    public function testBodyMultipartFormdataArrayOfBinaryAsync(
+        array $files,
+        string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0]
+    ): PromiseInterface
     {
         return $this->testBodyMultipartFormdataArrayOfBinaryAsyncWithHttpInfo($files, $contentType)
             ->then(
@@ -827,10 +863,13 @@ class BodyApi
      * @param  \SplFileObject[] $files (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyMultipartFormdataArrayOfBinary'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testBodyMultipartFormdataArrayOfBinaryAsyncWithHttpInfo($files, string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0])
+    public function testBodyMultipartFormdataArrayOfBinaryAsyncWithHttpInfo(
+        $files,
+        string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testBodyMultipartFormdataArrayOfBinaryRequest($files, $contentType);
@@ -877,15 +916,18 @@ class BodyApi
      * @param  \SplFileObject[] $files (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testBodyMultipartFormdataArrayOfBinary'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testBodyMultipartFormdataArrayOfBinaryRequest($files, string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0])
+    public function testBodyMultipartFormdataArrayOfBinaryRequest(
+        $files,
+        string $contentType = self::contentTypes['testBodyMultipartFormdataArrayOfBinary'][0]
+    ): Request
     {
 
         // verify the required parameter 'files' is set
         if ($files === null || (is_array($files) && count($files) === 0)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 'Missing the required parameter $files when calling testBodyMultipartFormdataArrayOfBinary'
             );
         }
@@ -972,14 +1014,17 @@ class BodyApi
      *
      * Test free form object
      *
-     * @param  object $body Free form object (optional)
+     * @param  object|null $body Free form object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyFreeFormObjectResponseString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testEchoBodyFreeFormObjectResponseString($body = null, string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0])
+    public function testEchoBodyFreeFormObjectResponseString(
+        ?array $body = null,
+        string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0]
+    ): string
     {
         list($response) = $this->testEchoBodyFreeFormObjectResponseStringWithHttpInfo($body, $contentType);
         return $response;
@@ -990,14 +1035,17 @@ class BodyApi
      *
      * Test free form object
      *
-     * @param  object $body Free form object (optional)
+     * @param  object|null $body Free form object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyFreeFormObjectResponseString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testEchoBodyFreeFormObjectResponseStringWithHttpInfo($body = null, string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0])
+    public function testEchoBodyFreeFormObjectResponseStringWithHttpInfo(
+        ?array $body = null,
+        string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0]
+    ): array
     {
         $request = $this->testEchoBodyFreeFormObjectResponseStringRequest($body, $contentType);
 
@@ -1090,13 +1138,16 @@ class BodyApi
      *
      * Test free form object
      *
-     * @param  object $body Free form object (optional)
+     * @param  object|null $body Free form object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyFreeFormObjectResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEchoBodyFreeFormObjectResponseStringAsync($body = null, string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0])
+    public function testEchoBodyFreeFormObjectResponseStringAsync(
+        ?array $body = null,
+        string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0]
+    ): PromiseInterface
     {
         return $this->testEchoBodyFreeFormObjectResponseStringAsyncWithHttpInfo($body, $contentType)
             ->then(
@@ -1111,13 +1162,16 @@ class BodyApi
      *
      * Test free form object
      *
-     * @param  object $body Free form object (optional)
+     * @param  object|null $body Free form object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyFreeFormObjectResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEchoBodyFreeFormObjectResponseStringAsyncWithHttpInfo($body = null, string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0])
+    public function testEchoBodyFreeFormObjectResponseStringAsyncWithHttpInfo(
+        $body = null,
+        string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testEchoBodyFreeFormObjectResponseStringRequest($body, $contentType);
@@ -1161,13 +1215,16 @@ class BodyApi
     /**
      * Create request for operation 'testEchoBodyFreeFormObjectResponseString'
      *
-     * @param  object $body Free form object (optional)
+     * @param  object|null $body Free form object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyFreeFormObjectResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testEchoBodyFreeFormObjectResponseStringRequest($body = null, string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0])
+    public function testEchoBodyFreeFormObjectResponseStringRequest(
+        $body = null,
+        string $contentType = self::contentTypes['testEchoBodyFreeFormObjectResponseString'][0]
+    ): Request
     {
 
 
@@ -1248,14 +1305,17 @@ class BodyApi
      *
      * Test body parameter(s)
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPet'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return \OpenAPI\Client\Model\Pet
      */
-    public function testEchoBodyPet($pet = null, string $contentType = self::contentTypes['testEchoBodyPet'][0])
+    public function testEchoBodyPet(
+        ?\OpenAPI\Client\Model\Pet $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPet'][0]
+    ): \OpenAPI\Client\Model\Pet
     {
         list($response) = $this->testEchoBodyPetWithHttpInfo($pet, $contentType);
         return $response;
@@ -1266,14 +1326,17 @@ class BodyApi
      *
      * Test body parameter(s)
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPet'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of \OpenAPI\Client\Model\Pet, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testEchoBodyPetWithHttpInfo($pet = null, string $contentType = self::contentTypes['testEchoBodyPet'][0])
+    public function testEchoBodyPetWithHttpInfo(
+        ?\OpenAPI\Client\Model\Pet $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPet'][0]
+    ): array
     {
         $request = $this->testEchoBodyPetRequest($pet, $contentType);
 
@@ -1366,13 +1429,16 @@ class BodyApi
      *
      * Test body parameter(s)
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPet'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEchoBodyPetAsync($pet = null, string $contentType = self::contentTypes['testEchoBodyPet'][0])
+    public function testEchoBodyPetAsync(
+        ?\OpenAPI\Client\Model\Pet $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPet'][0]
+    ): PromiseInterface
     {
         return $this->testEchoBodyPetAsyncWithHttpInfo($pet, $contentType)
             ->then(
@@ -1387,13 +1453,16 @@ class BodyApi
      *
      * Test body parameter(s)
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPet'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEchoBodyPetAsyncWithHttpInfo($pet = null, string $contentType = self::contentTypes['testEchoBodyPet'][0])
+    public function testEchoBodyPetAsyncWithHttpInfo(
+        $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPet'][0]
+    ): PromiseInterface
     {
         $returnType = '\OpenAPI\Client\Model\Pet';
         $request = $this->testEchoBodyPetRequest($pet, $contentType);
@@ -1437,13 +1506,16 @@ class BodyApi
     /**
      * Create request for operation 'testEchoBodyPet'
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPet'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testEchoBodyPetRequest($pet = null, string $contentType = self::contentTypes['testEchoBodyPet'][0])
+    public function testEchoBodyPetRequest(
+        $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPet'][0]
+    ): Request
     {
 
 
@@ -1524,14 +1596,17 @@ class BodyApi
      *
      * Test empty response body
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPetResponseString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testEchoBodyPetResponseString($pet = null, string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0])
+    public function testEchoBodyPetResponseString(
+        ?\OpenAPI\Client\Model\Pet $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0]
+    ): string
     {
         list($response) = $this->testEchoBodyPetResponseStringWithHttpInfo($pet, $contentType);
         return $response;
@@ -1542,14 +1617,17 @@ class BodyApi
      *
      * Test empty response body
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPetResponseString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testEchoBodyPetResponseStringWithHttpInfo($pet = null, string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0])
+    public function testEchoBodyPetResponseStringWithHttpInfo(
+        ?\OpenAPI\Client\Model\Pet $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0]
+    ): array
     {
         $request = $this->testEchoBodyPetResponseStringRequest($pet, $contentType);
 
@@ -1642,13 +1720,16 @@ class BodyApi
      *
      * Test empty response body
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPetResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEchoBodyPetResponseStringAsync($pet = null, string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0])
+    public function testEchoBodyPetResponseStringAsync(
+        ?\OpenAPI\Client\Model\Pet $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0]
+    ): PromiseInterface
     {
         return $this->testEchoBodyPetResponseStringAsyncWithHttpInfo($pet, $contentType)
             ->then(
@@ -1663,13 +1744,16 @@ class BodyApi
      *
      * Test empty response body
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPetResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEchoBodyPetResponseStringAsyncWithHttpInfo($pet = null, string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0])
+    public function testEchoBodyPetResponseStringAsyncWithHttpInfo(
+        $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testEchoBodyPetResponseStringRequest($pet, $contentType);
@@ -1713,13 +1797,16 @@ class BodyApi
     /**
      * Create request for operation 'testEchoBodyPetResponseString'
      *
-     * @param  \OpenAPI\Client\Model\Pet $pet Pet object that needs to be added to the store (optional)
+     * @param  \OpenAPI\Client\Model\Pet|null $pet Pet object that needs to be added to the store (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyPetResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testEchoBodyPetResponseStringRequest($pet = null, string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0])
+    public function testEchoBodyPetResponseStringRequest(
+        $pet = null,
+        string $contentType = self::contentTypes['testEchoBodyPetResponseString'][0]
+    ): Request
     {
 
 
@@ -1800,14 +1887,17 @@ class BodyApi
      *
      * Test empty json (request body)
      *
-     * @param  \OpenAPI\Client\Model\Tag $tag Tag object (optional)
+     * @param  \OpenAPI\Client\Model\Tag|null $tag Tag object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyTagResponseString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testEchoBodyTagResponseString($tag = null, string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0])
+    public function testEchoBodyTagResponseString(
+        ?\OpenAPI\Client\Model\Tag $tag = null,
+        string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0]
+    ): string
     {
         list($response) = $this->testEchoBodyTagResponseStringWithHttpInfo($tag, $contentType);
         return $response;
@@ -1818,14 +1908,17 @@ class BodyApi
      *
      * Test empty json (request body)
      *
-     * @param  \OpenAPI\Client\Model\Tag $tag Tag object (optional)
+     * @param  \OpenAPI\Client\Model\Tag|null $tag Tag object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyTagResponseString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testEchoBodyTagResponseStringWithHttpInfo($tag = null, string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0])
+    public function testEchoBodyTagResponseStringWithHttpInfo(
+        ?\OpenAPI\Client\Model\Tag $tag = null,
+        string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0]
+    ): array
     {
         $request = $this->testEchoBodyTagResponseStringRequest($tag, $contentType);
 
@@ -1918,13 +2011,16 @@ class BodyApi
      *
      * Test empty json (request body)
      *
-     * @param  \OpenAPI\Client\Model\Tag $tag Tag object (optional)
+     * @param  \OpenAPI\Client\Model\Tag|null $tag Tag object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyTagResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEchoBodyTagResponseStringAsync($tag = null, string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0])
+    public function testEchoBodyTagResponseStringAsync(
+        ?\OpenAPI\Client\Model\Tag $tag = null,
+        string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0]
+    ): PromiseInterface
     {
         return $this->testEchoBodyTagResponseStringAsyncWithHttpInfo($tag, $contentType)
             ->then(
@@ -1939,13 +2035,16 @@ class BodyApi
      *
      * Test empty json (request body)
      *
-     * @param  \OpenAPI\Client\Model\Tag $tag Tag object (optional)
+     * @param  \OpenAPI\Client\Model\Tag|null $tag Tag object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyTagResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEchoBodyTagResponseStringAsyncWithHttpInfo($tag = null, string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0])
+    public function testEchoBodyTagResponseStringAsyncWithHttpInfo(
+        $tag = null,
+        string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testEchoBodyTagResponseStringRequest($tag, $contentType);
@@ -1989,13 +2088,16 @@ class BodyApi
     /**
      * Create request for operation 'testEchoBodyTagResponseString'
      *
-     * @param  \OpenAPI\Client\Model\Tag $tag Tag object (optional)
+     * @param  \OpenAPI\Client\Model\Tag|null $tag Tag object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEchoBodyTagResponseString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testEchoBodyTagResponseStringRequest($tag = null, string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0])
+    public function testEchoBodyTagResponseStringRequest(
+        $tag = null,
+        string $contentType = self::contentTypes['testEchoBodyTagResponseString'][0]
+    ): Request
     {
 
 
@@ -2077,7 +2179,7 @@ class BodyApi
      * @throws \RuntimeException on file opening failure
      * @return array of http client options
      */
-    protected function createHttpClientOption()
+    protected function createHttpClientOption(): array
     {
         $options = [];
         if ($this->config->getDebug()) {

samples/client/echo_api/php-nextgen/src/Api/FormApi.php

@@ -28,6 +28,7 @@
 
 namespace OpenAPI\Client\Api;
 
+use InvalidArgumentException;
 use GuzzleHttp\Client;
 use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\ConnectException;
@@ -35,6 +36,7 @@ use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\RequestOptions;
+use GuzzleHttp\Promise\PromiseInterface;
 use OpenAPI\Client\ApiException;
 use OpenAPI\Client\Configuration;
 use OpenAPI\Client\HeaderSelector;
@@ -53,22 +55,22 @@ class FormApi
     /**
      * @var ClientInterface
      */
-    protected $client;
+    protected ClientInterface $client;
 
     /**
      * @var Configuration
      */
-    protected $config;
+    protected Configuration $config;
 
     /**
      * @var HeaderSelector
      */
-    protected $headerSelector;
+    protected HeaderSelector $headerSelector;
 
     /**
      * @var int Host index
      */
-    protected $hostIndex;
+    protected int $hostIndex;
 
     /** @var string[] $contentTypes **/
     public const contentTypes = [
@@ -81,16 +83,16 @@ class FormApi
     ];
 
     /**
-     * @param ClientInterface $client
-     * @param Configuration   $config
-     * @param HeaderSelector  $selector
+     * @param ClientInterface|null $client
+     * @param Configuration|null   $config
+     * @param HeaderSelector|null  $selector
      * @param int                  $hostIndex (Optional) host index to select the list of hosts if defined in the OpenAPI spec
      */
     public function __construct(
         ClientInterface $client = null,
         Configuration $config = null,
         HeaderSelector $selector = null,
-        $hostIndex = 0
+        int $hostIndex = 0
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -103,7 +105,7 @@ class FormApi
      *
      * @param int $hostIndex Host index (required)
      */
-    public function setHostIndex($hostIndex): void
+    public function setHostIndex(int $hostIndex): void
     {
         $this->hostIndex = $hostIndex;
     }
@@ -113,7 +115,7 @@ class FormApi
      *
      * @return int Host index
      */
-    public function getHostIndex()
+    public function getHostIndex(): int
     {
         return $this->hostIndex;
     }
@@ -121,7 +123,7 @@ class FormApi
     /**
      * @return Configuration
      */
-    public function getConfig()
+    public function getConfig(): Configuration
     {
         return $this->config;
     }
@@ -131,16 +133,21 @@ class FormApi
      *
      * Test form parameter(s)
      *
-     * @param  int $integer_form integer_form (optional)
-     * @param  bool $boolean_form boolean_form (optional)
-     * @param  string $string_form string_form (optional)
+     * @param  int|null $integer_form integer_form (optional)
+     * @param  bool|null $boolean_form boolean_form (optional)
+     * @param  string|null $string_form string_form (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testFormIntegerBooleanString($integer_form = null, $boolean_form = null, $string_form = null, string $contentType = self::contentTypes['testFormIntegerBooleanString'][0])
+    public function testFormIntegerBooleanString(
+        ?int $integer_form = null,
+        ?bool $boolean_form = null,
+        ?string $string_form = null,
+        string $contentType = self::contentTypes['testFormIntegerBooleanString'][0]
+    ): string
     {
         list($response) = $this->testFormIntegerBooleanStringWithHttpInfo($integer_form, $boolean_form, $string_form, $contentType);
         return $response;
@@ -151,16 +158,21 @@ class FormApi
      *
      * Test form parameter(s)
      *
-     * @param  int $integer_form (optional)
-     * @param  bool $boolean_form (optional)
-     * @param  string $string_form (optional)
+     * @param  int|null $integer_form (optional)
+     * @param  bool|null $boolean_form (optional)
+     * @param  string|null $string_form (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testFormIntegerBooleanStringWithHttpInfo($integer_form = null, $boolean_form = null, $string_form = null, string $contentType = self::contentTypes['testFormIntegerBooleanString'][0])
+    public function testFormIntegerBooleanStringWithHttpInfo(
+        ?int $integer_form = null,
+        ?bool $boolean_form = null,
+        ?string $string_form = null,
+        string $contentType = self::contentTypes['testFormIntegerBooleanString'][0]
+    ): array
     {
         $request = $this->testFormIntegerBooleanStringRequest($integer_form, $boolean_form, $string_form, $contentType);
 
@@ -253,15 +265,20 @@ class FormApi
      *
      * Test form parameter(s)
      *
-     * @param  int $integer_form (optional)
-     * @param  bool $boolean_form (optional)
-     * @param  string $string_form (optional)
+     * @param  int|null $integer_form (optional)
+     * @param  bool|null $boolean_form (optional)
+     * @param  string|null $string_form (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testFormIntegerBooleanStringAsync($integer_form = null, $boolean_form = null, $string_form = null, string $contentType = self::contentTypes['testFormIntegerBooleanString'][0])
+    public function testFormIntegerBooleanStringAsync(
+        ?int $integer_form = null,
+        ?bool $boolean_form = null,
+        ?string $string_form = null,
+        string $contentType = self::contentTypes['testFormIntegerBooleanString'][0]
+    ): PromiseInterface
     {
         return $this->testFormIntegerBooleanStringAsyncWithHttpInfo($integer_form, $boolean_form, $string_form, $contentType)
             ->then(
@@ -276,15 +293,20 @@ class FormApi
      *
      * Test form parameter(s)
      *
-     * @param  int $integer_form (optional)
-     * @param  bool $boolean_form (optional)
-     * @param  string $string_form (optional)
+     * @param  int|null $integer_form (optional)
+     * @param  bool|null $boolean_form (optional)
+     * @param  string|null $string_form (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testFormIntegerBooleanStringAsyncWithHttpInfo($integer_form = null, $boolean_form = null, $string_form = null, string $contentType = self::contentTypes['testFormIntegerBooleanString'][0])
+    public function testFormIntegerBooleanStringAsyncWithHttpInfo(
+        $integer_form = null,
+        $boolean_form = null,
+        $string_form = null,
+        string $contentType = self::contentTypes['testFormIntegerBooleanString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testFormIntegerBooleanStringRequest($integer_form, $boolean_form, $string_form, $contentType);
@@ -328,15 +350,20 @@ class FormApi
     /**
      * Create request for operation 'testFormIntegerBooleanString'
      *
-     * @param  int $integer_form (optional)
-     * @param  bool $boolean_form (optional)
-     * @param  string $string_form (optional)
+     * @param  int|null $integer_form (optional)
+     * @param  bool|null $boolean_form (optional)
+     * @param  string|null $string_form (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testFormIntegerBooleanStringRequest($integer_form = null, $boolean_form = null, $string_form = null, string $contentType = self::contentTypes['testFormIntegerBooleanString'][0])
+    public function testFormIntegerBooleanStringRequest(
+        $integer_form = null,
+        $boolean_form = null,
+        $string_form = null,
+        string $contentType = self::contentTypes['testFormIntegerBooleanString'][0]
+    ): Request
     {
 
 
@@ -424,19 +451,27 @@ class FormApi
      *
      * Test form parameter(s) for oneOf schema
      *
-     * @param  string $form1 form1 (optional)
-     * @param  int $form2 form2 (optional)
-     * @param  string $form3 form3 (optional)
-     * @param  bool $form4 form4 (optional)
-     * @param  int $id id (optional)
-     * @param  string $name name (optional)
+     * @param  string|null $form1 form1 (optional)
+     * @param  int|null $form2 form2 (optional)
+     * @param  string|null $form3 form3 (optional)
+     * @param  bool|null $form4 form4 (optional)
+     * @param  int|null $id id (optional)
+     * @param  string|null $name name (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormOneof'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testFormOneof($form1 = null, $form2 = null, $form3 = null, $form4 = null, $id = null, $name = null, string $contentType = self::contentTypes['testFormOneof'][0])
+    public function testFormOneof(
+        ?string $form1 = null,
+        ?int $form2 = null,
+        ?string $form3 = null,
+        ?bool $form4 = null,
+        ?int $id = null,
+        ?string $name = null,
+        string $contentType = self::contentTypes['testFormOneof'][0]
+    ): string
     {
         list($response) = $this->testFormOneofWithHttpInfo($form1, $form2, $form3, $form4, $id, $name, $contentType);
         return $response;
@@ -447,19 +482,27 @@ class FormApi
      *
      * Test form parameter(s) for oneOf schema
      *
-     * @param  string $form1 (optional)
-     * @param  int $form2 (optional)
-     * @param  string $form3 (optional)
-     * @param  bool $form4 (optional)
-     * @param  int $id (optional)
-     * @param  string $name (optional)
+     * @param  string|null $form1 (optional)
+     * @param  int|null $form2 (optional)
+     * @param  string|null $form3 (optional)
+     * @param  bool|null $form4 (optional)
+     * @param  int|null $id (optional)
+     * @param  string|null $name (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormOneof'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testFormOneofWithHttpInfo($form1 = null, $form2 = null, $form3 = null, $form4 = null, $id = null, $name = null, string $contentType = self::contentTypes['testFormOneof'][0])
+    public function testFormOneofWithHttpInfo(
+        ?string $form1 = null,
+        ?int $form2 = null,
+        ?string $form3 = null,
+        ?bool $form4 = null,
+        ?int $id = null,
+        ?string $name = null,
+        string $contentType = self::contentTypes['testFormOneof'][0]
+    ): array
     {
         $request = $this->testFormOneofRequest($form1, $form2, $form3, $form4, $id, $name, $contentType);
 
@@ -552,18 +595,26 @@ class FormApi
      *
      * Test form parameter(s) for oneOf schema
      *
-     * @param  string $form1 (optional)
-     * @param  int $form2 (optional)
-     * @param  string $form3 (optional)
-     * @param  bool $form4 (optional)
-     * @param  int $id (optional)
-     * @param  string $name (optional)
+     * @param  string|null $form1 (optional)
+     * @param  int|null $form2 (optional)
+     * @param  string|null $form3 (optional)
+     * @param  bool|null $form4 (optional)
+     * @param  int|null $id (optional)
+     * @param  string|null $name (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormOneof'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testFormOneofAsync($form1 = null, $form2 = null, $form3 = null, $form4 = null, $id = null, $name = null, string $contentType = self::contentTypes['testFormOneof'][0])
+    public function testFormOneofAsync(
+        ?string $form1 = null,
+        ?int $form2 = null,
+        ?string $form3 = null,
+        ?bool $form4 = null,
+        ?int $id = null,
+        ?string $name = null,
+        string $contentType = self::contentTypes['testFormOneof'][0]
+    ): PromiseInterface
     {
         return $this->testFormOneofAsyncWithHttpInfo($form1, $form2, $form3, $form4, $id, $name, $contentType)
             ->then(
@@ -578,18 +629,26 @@ class FormApi
      *
      * Test form parameter(s) for oneOf schema
      *
-     * @param  string $form1 (optional)
-     * @param  int $form2 (optional)
-     * @param  string $form3 (optional)
-     * @param  bool $form4 (optional)
-     * @param  int $id (optional)
-     * @param  string $name (optional)
+     * @param  string|null $form1 (optional)
+     * @param  int|null $form2 (optional)
+     * @param  string|null $form3 (optional)
+     * @param  bool|null $form4 (optional)
+     * @param  int|null $id (optional)
+     * @param  string|null $name (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormOneof'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testFormOneofAsyncWithHttpInfo($form1 = null, $form2 = null, $form3 = null, $form4 = null, $id = null, $name = null, string $contentType = self::contentTypes['testFormOneof'][0])
+    public function testFormOneofAsyncWithHttpInfo(
+        $form1 = null,
+        $form2 = null,
+        $form3 = null,
+        $form4 = null,
+        $id = null,
+        $name = null,
+        string $contentType = self::contentTypes['testFormOneof'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testFormOneofRequest($form1, $form2, $form3, $form4, $id, $name, $contentType);
@@ -633,18 +692,26 @@ class FormApi
     /**
      * Create request for operation 'testFormOneof'
      *
-     * @param  string $form1 (optional)
-     * @param  int $form2 (optional)
-     * @param  string $form3 (optional)
-     * @param  bool $form4 (optional)
-     * @param  int $id (optional)
-     * @param  string $name (optional)
+     * @param  string|null $form1 (optional)
+     * @param  int|null $form2 (optional)
+     * @param  string|null $form3 (optional)
+     * @param  bool|null $form4 (optional)
+     * @param  int|null $id (optional)
+     * @param  string|null $name (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testFormOneof'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testFormOneofRequest($form1 = null, $form2 = null, $form3 = null, $form4 = null, $id = null, $name = null, string $contentType = self::contentTypes['testFormOneof'][0])
+    public function testFormOneofRequest(
+        $form1 = null,
+        $form2 = null,
+        $form3 = null,
+        $form4 = null,
+        $id = null,
+        $name = null,
+        string $contentType = self::contentTypes['testFormOneof'][0]
+    ): Request
     {
 
 
@@ -748,7 +815,7 @@ class FormApi
      * @throws \RuntimeException on file opening failure
      * @return array of http client options
      */
-    protected function createHttpClientOption()
+    protected function createHttpClientOption(): array
     {
         $options = [];
         if ($this->config->getDebug()) {

samples/client/echo_api/php-nextgen/src/Api/HeaderApi.php

@@ -28,6 +28,7 @@
 
 namespace OpenAPI\Client\Api;
 
+use InvalidArgumentException;
 use GuzzleHttp\Client;
 use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\ConnectException;
@@ -35,6 +36,7 @@ use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\RequestOptions;
+use GuzzleHttp\Promise\PromiseInterface;
 use OpenAPI\Client\ApiException;
 use OpenAPI\Client\Configuration;
 use OpenAPI\Client\HeaderSelector;
@@ -53,22 +55,22 @@ class HeaderApi
     /**
      * @var ClientInterface
      */
-    protected $client;
+    protected ClientInterface $client;
 
     /**
      * @var Configuration
      */
-    protected $config;
+    protected Configuration $config;
 
     /**
      * @var HeaderSelector
      */
-    protected $headerSelector;
+    protected HeaderSelector $headerSelector;
 
     /**
      * @var int Host index
      */
-    protected $hostIndex;
+    protected int $hostIndex;
 
     /** @var string[] $contentTypes **/
     public const contentTypes = [
@@ -78,16 +80,16 @@ class HeaderApi
     ];
 
     /**
-     * @param ClientInterface $client
-     * @param Configuration   $config
-     * @param HeaderSelector  $selector
+     * @param ClientInterface|null $client
+     * @param Configuration|null   $config
+     * @param HeaderSelector|null  $selector
      * @param int                  $hostIndex (Optional) host index to select the list of hosts if defined in the OpenAPI spec
      */
     public function __construct(
         ClientInterface $client = null,
         Configuration $config = null,
         HeaderSelector $selector = null,
-        $hostIndex = 0
+        int $hostIndex = 0
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -100,7 +102,7 @@ class HeaderApi
      *
      * @param int $hostIndex Host index (required)
      */
-    public function setHostIndex($hostIndex): void
+    public function setHostIndex(int $hostIndex): void
     {
         $this->hostIndex = $hostIndex;
     }
@@ -110,7 +112,7 @@ class HeaderApi
      *
      * @return int Host index
      */
-    public function getHostIndex()
+    public function getHostIndex(): int
     {
         return $this->hostIndex;
     }
@@ -118,7 +120,7 @@ class HeaderApi
     /**
      * @return Configuration
      */
-    public function getConfig()
+    public function getConfig(): Configuration
     {
         return $this->config;
     }
@@ -128,16 +130,21 @@ class HeaderApi
      *
      * Test header parameter(s)
      *
-     * @param  int $integer_header integer_header (optional)
-     * @param  bool $boolean_header boolean_header (optional)
-     * @param  string $string_header string_header (optional)
+     * @param  int|null $integer_header integer_header (optional)
+     * @param  bool|null $boolean_header boolean_header (optional)
+     * @param  string|null $string_header string_header (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testHeaderIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testHeaderIntegerBooleanString($integer_header = null, $boolean_header = null, $string_header = null, string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0])
+    public function testHeaderIntegerBooleanString(
+        ?int $integer_header = null,
+        ?bool $boolean_header = null,
+        ?string $string_header = null,
+        string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0]
+    ): string
     {
         list($response) = $this->testHeaderIntegerBooleanStringWithHttpInfo($integer_header, $boolean_header, $string_header, $contentType);
         return $response;
@@ -148,16 +155,21 @@ class HeaderApi
      *
      * Test header parameter(s)
      *
-     * @param  int $integer_header (optional)
-     * @param  bool $boolean_header (optional)
-     * @param  string $string_header (optional)
+     * @param  int|null $integer_header (optional)
+     * @param  bool|null $boolean_header (optional)
+     * @param  string|null $string_header (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testHeaderIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testHeaderIntegerBooleanStringWithHttpInfo($integer_header = null, $boolean_header = null, $string_header = null, string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0])
+    public function testHeaderIntegerBooleanStringWithHttpInfo(
+        ?int $integer_header = null,
+        ?bool $boolean_header = null,
+        ?string $string_header = null,
+        string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0]
+    ): array
     {
         $request = $this->testHeaderIntegerBooleanStringRequest($integer_header, $boolean_header, $string_header, $contentType);
 
@@ -250,15 +262,20 @@ class HeaderApi
      *
      * Test header parameter(s)
      *
-     * @param  int $integer_header (optional)
-     * @param  bool $boolean_header (optional)
-     * @param  string $string_header (optional)
+     * @param  int|null $integer_header (optional)
+     * @param  bool|null $boolean_header (optional)
+     * @param  string|null $string_header (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testHeaderIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testHeaderIntegerBooleanStringAsync($integer_header = null, $boolean_header = null, $string_header = null, string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0])
+    public function testHeaderIntegerBooleanStringAsync(
+        ?int $integer_header = null,
+        ?bool $boolean_header = null,
+        ?string $string_header = null,
+        string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0]
+    ): PromiseInterface
     {
         return $this->testHeaderIntegerBooleanStringAsyncWithHttpInfo($integer_header, $boolean_header, $string_header, $contentType)
             ->then(
@@ -273,15 +290,20 @@ class HeaderApi
      *
      * Test header parameter(s)
      *
-     * @param  int $integer_header (optional)
-     * @param  bool $boolean_header (optional)
-     * @param  string $string_header (optional)
+     * @param  int|null $integer_header (optional)
+     * @param  bool|null $boolean_header (optional)
+     * @param  string|null $string_header (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testHeaderIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testHeaderIntegerBooleanStringAsyncWithHttpInfo($integer_header = null, $boolean_header = null, $string_header = null, string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0])
+    public function testHeaderIntegerBooleanStringAsyncWithHttpInfo(
+        $integer_header = null,
+        $boolean_header = null,
+        $string_header = null,
+        string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testHeaderIntegerBooleanStringRequest($integer_header, $boolean_header, $string_header, $contentType);
@@ -325,15 +347,20 @@ class HeaderApi
     /**
      * Create request for operation 'testHeaderIntegerBooleanString'
      *
-     * @param  int $integer_header (optional)
-     * @param  bool $boolean_header (optional)
-     * @param  string $string_header (optional)
+     * @param  int|null $integer_header (optional)
+     * @param  bool|null $boolean_header (optional)
+     * @param  string|null $string_header (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testHeaderIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testHeaderIntegerBooleanStringRequest($integer_header = null, $boolean_header = null, $string_header = null, string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0])
+    public function testHeaderIntegerBooleanStringRequest(
+        $integer_header = null,
+        $boolean_header = null,
+        $string_header = null,
+        string $contentType = self::contentTypes['testHeaderIntegerBooleanString'][0]
+    ): Request
     {
 
 
@@ -422,7 +449,7 @@ class HeaderApi
      * @throws \RuntimeException on file opening failure
      * @return array of http client options
      */
-    protected function createHttpClientOption()
+    protected function createHttpClientOption(): array
     {
         $options = [];
         if ($this->config->getDebug()) {

samples/client/echo_api/php-nextgen/src/Api/PathApi.php

@@ -28,6 +28,7 @@
 
 namespace OpenAPI\Client\Api;
 
+use InvalidArgumentException;
 use GuzzleHttp\Client;
 use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\ConnectException;
@@ -35,6 +36,7 @@ use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\RequestOptions;
+use GuzzleHttp\Promise\PromiseInterface;
 use OpenAPI\Client\ApiException;
 use OpenAPI\Client\Configuration;
 use OpenAPI\Client\HeaderSelector;
@@ -53,22 +55,22 @@ class PathApi
     /**
      * @var ClientInterface
      */
-    protected $client;
+    protected ClientInterface $client;
 
     /**
      * @var Configuration
      */
-    protected $config;
+    protected Configuration $config;
 
     /**
      * @var HeaderSelector
      */
-    protected $headerSelector;
+    protected HeaderSelector $headerSelector;
 
     /**
      * @var int Host index
      */
-    protected $hostIndex;
+    protected int $hostIndex;
 
     /** @var string[] $contentTypes **/
     public const contentTypes = [
@@ -78,16 +80,16 @@ class PathApi
     ];
 
     /**
-     * @param ClientInterface $client
-     * @param Configuration   $config
-     * @param HeaderSelector  $selector
+     * @param ClientInterface|null $client
+     * @param Configuration|null   $config
+     * @param HeaderSelector|null  $selector
      * @param int                  $hostIndex (Optional) host index to select the list of hosts if defined in the OpenAPI spec
      */
     public function __construct(
         ClientInterface $client = null,
         Configuration $config = null,
         HeaderSelector $selector = null,
-        $hostIndex = 0
+        int $hostIndex = 0
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -100,7 +102,7 @@ class PathApi
      *
      * @param int $hostIndex Host index (required)
      */
-    public function setHostIndex($hostIndex): void
+    public function setHostIndex(int $hostIndex): void
     {
         $this->hostIndex = $hostIndex;
     }
@@ -110,7 +112,7 @@ class PathApi
      *
      * @return int Host index
      */
-    public function getHostIndex()
+    public function getHostIndex(): int
     {
         return $this->hostIndex;
     }
@@ -118,7 +120,7 @@ class PathApi
     /**
      * @return Configuration
      */
-    public function getConfig()
+    public function getConfig(): Configuration
     {
         return $this->config;
     }
@@ -132,11 +134,15 @@ class PathApi
      * @param  int $path_integer path_integer (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testsPathStringPathStringIntegerPathInteger'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testsPathStringPathStringIntegerPathInteger($path_string, $path_integer, string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0])
+    public function testsPathStringPathStringIntegerPathInteger(
+        string $path_string,
+        int $path_integer,
+        string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0]
+    ): string
     {
         list($response) = $this->testsPathStringPathStringIntegerPathIntegerWithHttpInfo($path_string, $path_integer, $contentType);
         return $response;
@@ -151,11 +157,15 @@ class PathApi
      * @param  int $path_integer (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testsPathStringPathStringIntegerPathInteger'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testsPathStringPathStringIntegerPathIntegerWithHttpInfo($path_string, $path_integer, string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0])
+    public function testsPathStringPathStringIntegerPathIntegerWithHttpInfo(
+        string $path_string,
+        int $path_integer,
+        string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0]
+    ): array
     {
         $request = $this->testsPathStringPathStringIntegerPathIntegerRequest($path_string, $path_integer, $contentType);
 
@@ -252,10 +262,14 @@ class PathApi
      * @param  int $path_integer (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testsPathStringPathStringIntegerPathInteger'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testsPathStringPathStringIntegerPathIntegerAsync($path_string, $path_integer, string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0])
+    public function testsPathStringPathStringIntegerPathIntegerAsync(
+        string $path_string,
+        int $path_integer,
+        string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0]
+    ): PromiseInterface
     {
         return $this->testsPathStringPathStringIntegerPathIntegerAsyncWithHttpInfo($path_string, $path_integer, $contentType)
             ->then(
@@ -274,10 +288,14 @@ class PathApi
      * @param  int $path_integer (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testsPathStringPathStringIntegerPathInteger'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testsPathStringPathStringIntegerPathIntegerAsyncWithHttpInfo($path_string, $path_integer, string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0])
+    public function testsPathStringPathStringIntegerPathIntegerAsyncWithHttpInfo(
+        $path_string,
+        $path_integer,
+        string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testsPathStringPathStringIntegerPathIntegerRequest($path_string, $path_integer, $contentType);
@@ -325,22 +343,26 @@ class PathApi
      * @param  int $path_integer (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testsPathStringPathStringIntegerPathInteger'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testsPathStringPathStringIntegerPathIntegerRequest($path_string, $path_integer, string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0])
+    public function testsPathStringPathStringIntegerPathIntegerRequest(
+        $path_string,
+        $path_integer,
+        string $contentType = self::contentTypes['testsPathStringPathStringIntegerPathInteger'][0]
+    ): Request
     {
 
         // verify the required parameter 'path_string' is set
         if ($path_string === null || (is_array($path_string) && count($path_string) === 0)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 'Missing the required parameter $path_string when calling testsPathStringPathStringIntegerPathInteger'
             );
         }
 
         // verify the required parameter 'path_integer' is set
         if ($path_integer === null || (is_array($path_integer) && count($path_integer) === 0)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 'Missing the required parameter $path_integer when calling testsPathStringPathStringIntegerPathInteger'
             );
         }
@@ -432,7 +454,7 @@ class PathApi
      * @throws \RuntimeException on file opening failure
      * @return array of http client options
      */
-    protected function createHttpClientOption()
+    protected function createHttpClientOption(): array
     {
         $options = [];
         if ($this->config->getDebug()) {

samples/client/echo_api/php-nextgen/src/Api/QueryApi.php

@@ -28,6 +28,7 @@
 
 namespace OpenAPI\Client\Api;
 
+use InvalidArgumentException;
 use GuzzleHttp\Client;
 use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\ConnectException;
@@ -35,6 +36,7 @@ use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\RequestOptions;
+use GuzzleHttp\Promise\PromiseInterface;
 use OpenAPI\Client\ApiException;
 use OpenAPI\Client\Configuration;
 use OpenAPI\Client\HeaderSelector;
@@ -53,22 +55,22 @@ class QueryApi
     /**
      * @var ClientInterface
      */
-    protected $client;
+    protected ClientInterface $client;
 
     /**
      * @var Configuration
      */
-    protected $config;
+    protected Configuration $config;
 
     /**
      * @var HeaderSelector
      */
-    protected $headerSelector;
+    protected HeaderSelector $headerSelector;
 
     /**
      * @var int Host index
      */
-    protected $hostIndex;
+    protected int $hostIndex;
 
     /** @var string[] $contentTypes **/
     public const contentTypes = [
@@ -99,16 +101,16 @@ class QueryApi
     ];
 
     /**
-     * @param ClientInterface $client
-     * @param Configuration   $config
-     * @param HeaderSelector  $selector
+     * @param ClientInterface|null $client
+     * @param Configuration|null   $config
+     * @param HeaderSelector|null  $selector
      * @param int                  $hostIndex (Optional) host index to select the list of hosts if defined in the OpenAPI spec
      */
     public function __construct(
         ClientInterface $client = null,
         Configuration $config = null,
         HeaderSelector $selector = null,
-        $hostIndex = 0
+        int $hostIndex = 0
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -121,7 +123,7 @@ class QueryApi
      *
      * @param int $hostIndex Host index (required)
      */
-    public function setHostIndex($hostIndex): void
+    public function setHostIndex(int $hostIndex): void
     {
         $this->hostIndex = $hostIndex;
     }
@@ -131,7 +133,7 @@ class QueryApi
      *
      * @return int Host index
      */
-    public function getHostIndex()
+    public function getHostIndex(): int
     {
         return $this->hostIndex;
     }
@@ -139,7 +141,7 @@ class QueryApi
     /**
      * @return Configuration
      */
-    public function getConfig()
+    public function getConfig(): Configuration
     {
         return $this->config;
     }
@@ -149,14 +151,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  StringEnumRef $enum_ref_string_query enum_ref_string_query (optional)
+     * @param  StringEnumRef|null $enum_ref_string_query enum_ref_string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEnumRefString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testEnumRefString($enum_ref_string_query = null, string $contentType = self::contentTypes['testEnumRefString'][0])
+    public function testEnumRefString(
+        ?StringEnumRef $enum_ref_string_query = null,
+        string $contentType = self::contentTypes['testEnumRefString'][0]
+    ): string
     {
         list($response) = $this->testEnumRefStringWithHttpInfo($enum_ref_string_query, $contentType);
         return $response;
@@ -167,14 +172,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  StringEnumRef $enum_ref_string_query (optional)
+     * @param  StringEnumRef|null $enum_ref_string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEnumRefString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testEnumRefStringWithHttpInfo($enum_ref_string_query = null, string $contentType = self::contentTypes['testEnumRefString'][0])
+    public function testEnumRefStringWithHttpInfo(
+        ?StringEnumRef $enum_ref_string_query = null,
+        string $contentType = self::contentTypes['testEnumRefString'][0]
+    ): array
     {
         $request = $this->testEnumRefStringRequest($enum_ref_string_query, $contentType);
 
@@ -267,13 +275,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  StringEnumRef $enum_ref_string_query (optional)
+     * @param  StringEnumRef|null $enum_ref_string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEnumRefString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEnumRefStringAsync($enum_ref_string_query = null, string $contentType = self::contentTypes['testEnumRefString'][0])
+    public function testEnumRefStringAsync(
+        ?StringEnumRef $enum_ref_string_query = null,
+        string $contentType = self::contentTypes['testEnumRefString'][0]
+    ): PromiseInterface
     {
         return $this->testEnumRefStringAsyncWithHttpInfo($enum_ref_string_query, $contentType)
             ->then(
@@ -288,13 +299,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  StringEnumRef $enum_ref_string_query (optional)
+     * @param  StringEnumRef|null $enum_ref_string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEnumRefString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testEnumRefStringAsyncWithHttpInfo($enum_ref_string_query = null, string $contentType = self::contentTypes['testEnumRefString'][0])
+    public function testEnumRefStringAsyncWithHttpInfo(
+        $enum_ref_string_query = null,
+        string $contentType = self::contentTypes['testEnumRefString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testEnumRefStringRequest($enum_ref_string_query, $contentType);
@@ -338,13 +352,16 @@ class QueryApi
     /**
      * Create request for operation 'testEnumRefString'
      *
-     * @param  StringEnumRef $enum_ref_string_query (optional)
+     * @param  StringEnumRef|null $enum_ref_string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testEnumRefString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testEnumRefStringRequest($enum_ref_string_query = null, string $contentType = self::contentTypes['testEnumRefString'][0])
+    public function testEnumRefStringRequest(
+        $enum_ref_string_query = null,
+        string $contentType = self::contentTypes['testEnumRefString'][0]
+    ): Request
     {
 
 
@@ -427,16 +444,21 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  \DateTime $datetime_query datetime_query (optional)
-     * @param  \DateTime $date_query date_query (optional)
-     * @param  string $string_query string_query (optional)
+     * @param  \DateTime|null $datetime_query datetime_query (optional)
+     * @param  \DateTime|null $date_query date_query (optional)
+     * @param  string|null $string_query string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryDatetimeDateString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testQueryDatetimeDateString($datetime_query = null, $date_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryDatetimeDateString'][0])
+    public function testQueryDatetimeDateString(
+        ?\DateTime $datetime_query = null,
+        ?\DateTime $date_query = null,
+        ?string $string_query = null,
+        string $contentType = self::contentTypes['testQueryDatetimeDateString'][0]
+    ): string
     {
         list($response) = $this->testQueryDatetimeDateStringWithHttpInfo($datetime_query, $date_query, $string_query, $contentType);
         return $response;
@@ -447,16 +469,21 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  \DateTime $datetime_query (optional)
-     * @param  \DateTime $date_query (optional)
-     * @param  string $string_query (optional)
+     * @param  \DateTime|null $datetime_query (optional)
+     * @param  \DateTime|null $date_query (optional)
+     * @param  string|null $string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryDatetimeDateString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testQueryDatetimeDateStringWithHttpInfo($datetime_query = null, $date_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryDatetimeDateString'][0])
+    public function testQueryDatetimeDateStringWithHttpInfo(
+        ?\DateTime $datetime_query = null,
+        ?\DateTime $date_query = null,
+        ?string $string_query = null,
+        string $contentType = self::contentTypes['testQueryDatetimeDateString'][0]
+    ): array
     {
         $request = $this->testQueryDatetimeDateStringRequest($datetime_query, $date_query, $string_query, $contentType);
 
@@ -549,15 +576,20 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  \DateTime $datetime_query (optional)
-     * @param  \DateTime $date_query (optional)
-     * @param  string $string_query (optional)
+     * @param  \DateTime|null $datetime_query (optional)
+     * @param  \DateTime|null $date_query (optional)
+     * @param  string|null $string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryDatetimeDateString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryDatetimeDateStringAsync($datetime_query = null, $date_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryDatetimeDateString'][0])
+    public function testQueryDatetimeDateStringAsync(
+        ?\DateTime $datetime_query = null,
+        ?\DateTime $date_query = null,
+        ?string $string_query = null,
+        string $contentType = self::contentTypes['testQueryDatetimeDateString'][0]
+    ): PromiseInterface
     {
         return $this->testQueryDatetimeDateStringAsyncWithHttpInfo($datetime_query, $date_query, $string_query, $contentType)
             ->then(
@@ -572,15 +604,20 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  \DateTime $datetime_query (optional)
-     * @param  \DateTime $date_query (optional)
-     * @param  string $string_query (optional)
+     * @param  \DateTime|null $datetime_query (optional)
+     * @param  \DateTime|null $date_query (optional)
+     * @param  string|null $string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryDatetimeDateString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryDatetimeDateStringAsyncWithHttpInfo($datetime_query = null, $date_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryDatetimeDateString'][0])
+    public function testQueryDatetimeDateStringAsyncWithHttpInfo(
+        $datetime_query = null,
+        $date_query = null,
+        $string_query = null,
+        string $contentType = self::contentTypes['testQueryDatetimeDateString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testQueryDatetimeDateStringRequest($datetime_query, $date_query, $string_query, $contentType);
@@ -624,15 +661,20 @@ class QueryApi
     /**
      * Create request for operation 'testQueryDatetimeDateString'
      *
-     * @param  \DateTime $datetime_query (optional)
-     * @param  \DateTime $date_query (optional)
-     * @param  string $string_query (optional)
+     * @param  \DateTime|null $datetime_query (optional)
+     * @param  \DateTime|null $date_query (optional)
+     * @param  string|null $string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryDatetimeDateString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testQueryDatetimeDateStringRequest($datetime_query = null, $date_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryDatetimeDateString'][0])
+    public function testQueryDatetimeDateStringRequest(
+        $datetime_query = null,
+        $date_query = null,
+        $string_query = null,
+        string $contentType = self::contentTypes['testQueryDatetimeDateString'][0]
+    ): Request
     {
 
 
@@ -735,16 +777,21 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  int $integer_query integer_query (optional)
-     * @param  bool $boolean_query boolean_query (optional)
-     * @param  string $string_query string_query (optional)
+     * @param  int|null $integer_query integer_query (optional)
+     * @param  bool|null $boolean_query boolean_query (optional)
+     * @param  string|null $string_query string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testQueryIntegerBooleanString($integer_query = null, $boolean_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0])
+    public function testQueryIntegerBooleanString(
+        ?int $integer_query = null,
+        ?bool $boolean_query = null,
+        ?string $string_query = null,
+        string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0]
+    ): string
     {
         list($response) = $this->testQueryIntegerBooleanStringWithHttpInfo($integer_query, $boolean_query, $string_query, $contentType);
         return $response;
@@ -755,16 +802,21 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  int $integer_query (optional)
-     * @param  bool $boolean_query (optional)
-     * @param  string $string_query (optional)
+     * @param  int|null $integer_query (optional)
+     * @param  bool|null $boolean_query (optional)
+     * @param  string|null $string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testQueryIntegerBooleanStringWithHttpInfo($integer_query = null, $boolean_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0])
+    public function testQueryIntegerBooleanStringWithHttpInfo(
+        ?int $integer_query = null,
+        ?bool $boolean_query = null,
+        ?string $string_query = null,
+        string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0]
+    ): array
     {
         $request = $this->testQueryIntegerBooleanStringRequest($integer_query, $boolean_query, $string_query, $contentType);
 
@@ -857,15 +909,20 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  int $integer_query (optional)
-     * @param  bool $boolean_query (optional)
-     * @param  string $string_query (optional)
+     * @param  int|null $integer_query (optional)
+     * @param  bool|null $boolean_query (optional)
+     * @param  string|null $string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryIntegerBooleanStringAsync($integer_query = null, $boolean_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0])
+    public function testQueryIntegerBooleanStringAsync(
+        ?int $integer_query = null,
+        ?bool $boolean_query = null,
+        ?string $string_query = null,
+        string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0]
+    ): PromiseInterface
     {
         return $this->testQueryIntegerBooleanStringAsyncWithHttpInfo($integer_query, $boolean_query, $string_query, $contentType)
             ->then(
@@ -880,15 +937,20 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  int $integer_query (optional)
-     * @param  bool $boolean_query (optional)
-     * @param  string $string_query (optional)
+     * @param  int|null $integer_query (optional)
+     * @param  bool|null $boolean_query (optional)
+     * @param  string|null $string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryIntegerBooleanStringAsyncWithHttpInfo($integer_query = null, $boolean_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0])
+    public function testQueryIntegerBooleanStringAsyncWithHttpInfo(
+        $integer_query = null,
+        $boolean_query = null,
+        $string_query = null,
+        string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testQueryIntegerBooleanStringRequest($integer_query, $boolean_query, $string_query, $contentType);
@@ -932,15 +994,20 @@ class QueryApi
     /**
      * Create request for operation 'testQueryIntegerBooleanString'
      *
-     * @param  int $integer_query (optional)
-     * @param  bool $boolean_query (optional)
-     * @param  string $string_query (optional)
+     * @param  int|null $integer_query (optional)
+     * @param  bool|null $boolean_query (optional)
+     * @param  string|null $string_query (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryIntegerBooleanString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testQueryIntegerBooleanStringRequest($integer_query = null, $boolean_query = null, $string_query = null, string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0])
+    public function testQueryIntegerBooleanStringRequest(
+        $integer_query = null,
+        $boolean_query = null,
+        $string_query = null,
+        string $contentType = self::contentTypes['testQueryIntegerBooleanString'][0]
+    ): Request
     {
 
 
@@ -1043,14 +1110,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  Pet $query_object query_object (optional)
+     * @param  Pet|null $query_object query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testQueryStyleDeepObjectExplodeTrueObject($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObject(
+        ?Pet $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0]
+    ): string
     {
         list($response) = $this->testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo($query_object, $contentType);
         return $response;
@@ -1061,14 +1131,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  Pet $query_object (optional)
+     * @param  Pet|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectWithHttpInfo(
+        ?Pet $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0]
+    ): array
     {
         $request = $this->testQueryStyleDeepObjectExplodeTrueObjectRequest($query_object, $contentType);
 
@@ -1161,13 +1234,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  Pet $query_object (optional)
+     * @param  Pet|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectAsync($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectAsync(
+        ?Pet $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0]
+    ): PromiseInterface
     {
         return $this->testQueryStyleDeepObjectExplodeTrueObjectAsyncWithHttpInfo($query_object, $contentType)
             ->then(
@@ -1182,13 +1258,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  Pet $query_object (optional)
+     * @param  Pet|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectAsyncWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectAsyncWithHttpInfo(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testQueryStyleDeepObjectExplodeTrueObjectRequest($query_object, $contentType);
@@ -1232,13 +1311,16 @@ class QueryApi
     /**
      * Create request for operation 'testQueryStyleDeepObjectExplodeTrueObject'
      *
-     * @param  Pet $query_object (optional)
+     * @param  Pet|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectRequest($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectRequest(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObject'][0]
+    ): Request
     {
 
 
@@ -1321,14 +1403,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter $query_object query_object (optional)
+     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter|null $query_object query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectAllOf($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectAllOf(
+        ?TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0]
+    ): string
     {
         list($response) = $this->testQueryStyleDeepObjectExplodeTrueObjectAllOfWithHttpInfo($query_object, $contentType);
         return $response;
@@ -1339,14 +1424,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter $query_object (optional)
+     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectAllOfWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectAllOfWithHttpInfo(
+        ?TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0]
+    ): array
     {
         $request = $this->testQueryStyleDeepObjectExplodeTrueObjectAllOfRequest($query_object, $contentType);
 
@@ -1439,13 +1527,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter $query_object (optional)
+     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectAllOfAsync($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectAllOfAsync(
+        ?TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0]
+    ): PromiseInterface
     {
         return $this->testQueryStyleDeepObjectExplodeTrueObjectAllOfAsyncWithHttpInfo($query_object, $contentType)
             ->then(
@@ -1460,13 +1551,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter $query_object (optional)
+     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectAllOfAsyncWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectAllOfAsyncWithHttpInfo(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testQueryStyleDeepObjectExplodeTrueObjectAllOfRequest($query_object, $contentType);
@@ -1510,13 +1604,16 @@ class QueryApi
     /**
      * Create request for operation 'testQueryStyleDeepObjectExplodeTrueObjectAllOf'
      *
-     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter $query_object (optional)
+     * @param  TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testQueryStyleDeepObjectExplodeTrueObjectAllOfRequest($query_object = null, string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleDeepObjectExplodeTrueObjectAllOfRequest(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleDeepObjectExplodeTrueObjectAllOf'][0]
+    ): Request
     {
 
 
@@ -1599,14 +1696,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter $query_object query_object (optional)
+     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter|null $query_object query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueArrayString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testQueryStyleFormExplodeTrueArrayString($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0])
+    public function testQueryStyleFormExplodeTrueArrayString(
+        ?TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0]
+    ): string
     {
         list($response) = $this->testQueryStyleFormExplodeTrueArrayStringWithHttpInfo($query_object, $contentType);
         return $response;
@@ -1617,14 +1717,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter $query_object (optional)
+     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueArrayString'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testQueryStyleFormExplodeTrueArrayStringWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0])
+    public function testQueryStyleFormExplodeTrueArrayStringWithHttpInfo(
+        ?TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0]
+    ): array
     {
         $request = $this->testQueryStyleFormExplodeTrueArrayStringRequest($query_object, $contentType);
 
@@ -1717,13 +1820,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter $query_object (optional)
+     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueArrayString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleFormExplodeTrueArrayStringAsync($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0])
+    public function testQueryStyleFormExplodeTrueArrayStringAsync(
+        ?TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0]
+    ): PromiseInterface
     {
         return $this->testQueryStyleFormExplodeTrueArrayStringAsyncWithHttpInfo($query_object, $contentType)
             ->then(
@@ -1738,13 +1844,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter $query_object (optional)
+     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueArrayString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleFormExplodeTrueArrayStringAsyncWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0])
+    public function testQueryStyleFormExplodeTrueArrayStringAsyncWithHttpInfo(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testQueryStyleFormExplodeTrueArrayStringRequest($query_object, $contentType);
@@ -1788,13 +1897,16 @@ class QueryApi
     /**
      * Create request for operation 'testQueryStyleFormExplodeTrueArrayString'
      *
-     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter $query_object (optional)
+     * @param  TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueArrayString'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testQueryStyleFormExplodeTrueArrayStringRequest($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0])
+    public function testQueryStyleFormExplodeTrueArrayStringRequest(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueArrayString'][0]
+    ): Request
     {
 
 
@@ -1877,14 +1989,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  Pet $query_object query_object (optional)
+     * @param  Pet|null $query_object query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testQueryStyleFormExplodeTrueObject($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0])
+    public function testQueryStyleFormExplodeTrueObject(
+        ?Pet $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0]
+    ): string
     {
         list($response) = $this->testQueryStyleFormExplodeTrueObjectWithHttpInfo($query_object, $contentType);
         return $response;
@@ -1895,14 +2010,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  Pet $query_object (optional)
+     * @param  Pet|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testQueryStyleFormExplodeTrueObjectWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0])
+    public function testQueryStyleFormExplodeTrueObjectWithHttpInfo(
+        ?Pet $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0]
+    ): array
     {
         $request = $this->testQueryStyleFormExplodeTrueObjectRequest($query_object, $contentType);
 
@@ -1995,13 +2113,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  Pet $query_object (optional)
+     * @param  Pet|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleFormExplodeTrueObjectAsync($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0])
+    public function testQueryStyleFormExplodeTrueObjectAsync(
+        ?Pet $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0]
+    ): PromiseInterface
     {
         return $this->testQueryStyleFormExplodeTrueObjectAsyncWithHttpInfo($query_object, $contentType)
             ->then(
@@ -2016,13 +2137,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  Pet $query_object (optional)
+     * @param  Pet|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleFormExplodeTrueObjectAsyncWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0])
+    public function testQueryStyleFormExplodeTrueObjectAsyncWithHttpInfo(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testQueryStyleFormExplodeTrueObjectRequest($query_object, $contentType);
@@ -2066,13 +2190,16 @@ class QueryApi
     /**
      * Create request for operation 'testQueryStyleFormExplodeTrueObject'
      *
-     * @param  Pet $query_object (optional)
+     * @param  Pet|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObject'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testQueryStyleFormExplodeTrueObjectRequest($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0])
+    public function testQueryStyleFormExplodeTrueObjectRequest(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObject'][0]
+    ): Request
     {
 
 
@@ -2155,14 +2282,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  DataQuery $query_object query_object (optional)
+     * @param  DataQuery|null $query_object query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return string
      */
-    public function testQueryStyleFormExplodeTrueObjectAllOf($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleFormExplodeTrueObjectAllOf(
+        ?DataQuery $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0]
+    ): string
     {
         list($response) = $this->testQueryStyleFormExplodeTrueObjectAllOfWithHttpInfo($query_object, $contentType);
         return $response;
@@ -2173,14 +2303,17 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  DataQuery $query_object (optional)
+     * @param  DataQuery|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of string, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testQueryStyleFormExplodeTrueObjectAllOfWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleFormExplodeTrueObjectAllOfWithHttpInfo(
+        ?DataQuery $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0]
+    ): array
     {
         $request = $this->testQueryStyleFormExplodeTrueObjectAllOfRequest($query_object, $contentType);
 
@@ -2273,13 +2406,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  DataQuery $query_object (optional)
+     * @param  DataQuery|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleFormExplodeTrueObjectAllOfAsync($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleFormExplodeTrueObjectAllOfAsync(
+        ?DataQuery $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0]
+    ): PromiseInterface
     {
         return $this->testQueryStyleFormExplodeTrueObjectAllOfAsyncWithHttpInfo($query_object, $contentType)
             ->then(
@@ -2294,13 +2430,16 @@ class QueryApi
      *
      * Test query parameter(s)
      *
-     * @param  DataQuery $query_object (optional)
+     * @param  DataQuery|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testQueryStyleFormExplodeTrueObjectAllOfAsyncWithHttpInfo($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleFormExplodeTrueObjectAllOfAsyncWithHttpInfo(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0]
+    ): PromiseInterface
     {
         $returnType = 'string';
         $request = $this->testQueryStyleFormExplodeTrueObjectAllOfRequest($query_object, $contentType);
@@ -2344,13 +2483,16 @@ class QueryApi
     /**
      * Create request for operation 'testQueryStyleFormExplodeTrueObjectAllOf'
      *
-     * @param  DataQuery $query_object (optional)
+     * @param  DataQuery|null $query_object (optional)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testQueryStyleFormExplodeTrueObjectAllOfRequest($query_object = null, string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0])
+    public function testQueryStyleFormExplodeTrueObjectAllOfRequest(
+        $query_object = null,
+        string $contentType = self::contentTypes['testQueryStyleFormExplodeTrueObjectAllOf'][0]
+    ): Request
     {
 
 
@@ -2434,7 +2576,7 @@ class QueryApi
      * @throws \RuntimeException on file opening failure
      * @return array of http client options
      */
-    protected function createHttpClientOption()
+    protected function createHttpClientOption(): array
     {
         $options = [];
         if ($this->config->getDebug()) {

samples/client/echo_api/php-nextgen/src/ApiException.php

@@ -28,7 +28,8 @@
 
 namespace OpenAPI\Client;
 
-use \Exception;
+use Exception;
+use stdClass;
 
 /**
  * ApiException Class Doc Comment
@@ -43,23 +44,23 @@ class ApiException extends Exception
     /**
      * The HTTP body of the server response either as Json or string.
      *
-     * @var \stdClass|string|null
+     * @var stdClass|string|null
      */
-    protected $responseBody;
+    protected stdClass|string|null $responseBody;
 
     /**
      * The HTTP header of the server response.
      *
      * @var string[]|null
      */
-    protected $responseHeaders;
+    protected ?array $responseHeaders;
 
     /**
      * The deserialized response object
      *
-     * @var \stdClass|string|null
+     * @var mixed
      */
-    protected $responseObject;
+    protected mixed $responseObject;
 
     /**
      * Constructor
@@ -67,9 +68,9 @@ class ApiException extends Exception
      * @param string                $message         Error message
      * @param int                   $code            HTTP status code
      * @param string[]|null         $responseHeaders HTTP response header
-     * @param \stdClass|string|null $responseBody    HTTP decoded body of the server response either as \stdClass or string
+     * @param mixed $responseBody    HTTP decoded body of the server response either as stdClass or string
      */
-    public function __construct($message = "", $code = 0, $responseHeaders = [], $responseBody = null)
+    public function __construct(string $message = "", int $code = 0, ?array $responseHeaders = [], mixed $responseBody = null)
     {
         parent::__construct($message, $code);
         $this->responseHeaders = $responseHeaders;
@@ -81,7 +82,7 @@ class ApiException extends Exception
      *
      * @return string[]|null HTTP response header
      */
-    public function getResponseHeaders()
+    public function getResponseHeaders(): ?array
     {
         return $this->responseHeaders;
     }
@@ -89,9 +90,9 @@ class ApiException extends Exception
     /**
      * Gets the HTTP body of the server response either as Json or string
      *
-     * @return \stdClass|string|null HTTP body of the server response either as \stdClass or string
+     * @return stdClass|string|null HTTP body of the server response either as \stdClass or string
      */
-    public function getResponseBody()
+    public function getResponseBody(): stdClass|string|null
     {
         return $this->responseBody;
     }
@@ -103,7 +104,7 @@ class ApiException extends Exception
      *
      * @return void
      */
-    public function setResponseObject($obj)
+    public function setResponseObject(mixed $obj): void
     {
         $this->responseObject = $obj;
     }
@@ -113,7 +114,7 @@ class ApiException extends Exception
      *
      * @return mixed the deserialized response object
      */
-    public function getResponseObject()
+    public function getResponseObject(): mixed
     {
         return $this->responseObject;
     }

samples/client/echo_api/php-nextgen/src/Configuration.php

@@ -28,6 +28,8 @@
 
 namespace OpenAPI\Client;
 
+use InvalidArgumentException;
+
 /**
  * Configuration Class Doc Comment
  *
@@ -42,86 +44,86 @@ class Configuration
     public const BOOLEAN_FORMAT_STRING = 'string';
 
     /**
-     * @var Configuration
+     * @var Configuration|null
      */
-    private static $defaultConfiguration;
+    private static ?Configuration $defaultConfiguration = null;
 
     /**
      * Associate array to store API key(s)
      *
      * @var string[]
      */
-    protected $apiKeys = [];
+    protected array $apiKeys = [];
 
     /**
      * Associate array to store API prefix (e.g. Bearer)
      *
      * @var string[]
      */
-    protected $apiKeyPrefixes = [];
+    protected array $apiKeyPrefixes = [];
 
     /**
      * Access token for OAuth/Bearer authentication
      *
      * @var string
      */
-    protected $accessToken = '';
+    protected string $accessToken = '';
 
     /**
      * Boolean format for query string
      *
      * @var string
      */
-    protected $booleanFormatForQueryString = self::BOOLEAN_FORMAT_INT;
+    protected string $booleanFormatForQueryString = self::BOOLEAN_FORMAT_INT;
 
     /**
      * Username for HTTP basic authentication
      *
      * @var string
      */
-    protected $username = '';
+    protected string $username = '';
 
     /**
      * Password for HTTP basic authentication
      *
      * @var string
      */
-    protected $password = '';
+    protected string $password = '';
 
     /**
      * The host
      *
      * @var string
      */
-    protected $host = 'http://localhost:3000';
+    protected string $host = 'http://localhost:3000';
 
     /**
      * User agent of the HTTP request, set to "OpenAPI-Generator/{version}/PHP" by default
      *
      * @var string
      */
-    protected $userAgent = 'OpenAPI-Generator/1.0.0/PHP';
+    protected string $userAgent = 'OpenAPI-Generator/1.0.0/PHP';
 
     /**
      * Debug switch (default set to false)
      *
      * @var bool
      */
-    protected $debug = false;
+    protected bool $debug = false;
 
     /**
      * Debug file location (log to STDOUT by default)
      *
      * @var string
      */
-    protected $debugFile = 'php://output';
+    protected string $debugFile = 'php://output';
 
     /**
      * Debug file location (log to STDOUT by default)
      *
      * @var string
      */
-    protected $tempFolderPath;
+    protected string $tempFolderPath;
 
     /**
      * Constructor
@@ -139,7 +141,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setApiKey($apiKeyIdentifier, $key)
+    public function setApiKey(string $apiKeyIdentifier, string $key): static
     {
         $this->apiKeys[$apiKeyIdentifier] = $key;
         return $this;
@@ -152,9 +154,9 @@ class Configuration
      *
      * @return null|string API key or token
      */
-    public function getApiKey($apiKeyIdentifier)
+    public function getApiKey(string $apiKeyIdentifier): ?string
     {
-        return isset($this->apiKeys[$apiKeyIdentifier]) ? $this->apiKeys[$apiKeyIdentifier] : null;
+        return $this->apiKeys[$apiKeyIdentifier] ?? null;
     }
 
     /**
@@ -165,7 +167,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setApiKeyPrefix($apiKeyIdentifier, $prefix)
+    public function setApiKeyPrefix(string $apiKeyIdentifier, string $prefix): static
     {
         $this->apiKeyPrefixes[$apiKeyIdentifier] = $prefix;
         return $this;
@@ -178,9 +180,9 @@ class Configuration
      *
      * @return null|string
      */
-    public function getApiKeyPrefix($apiKeyIdentifier)
+    public function getApiKeyPrefix(string $apiKeyIdentifier): ?string
     {
-        return isset($this->apiKeyPrefixes[$apiKeyIdentifier]) ? $this->apiKeyPrefixes[$apiKeyIdentifier] : null;
+        return $this->apiKeyPrefixes[$apiKeyIdentifier] ?? null;
     }
 
     /**
@@ -190,7 +192,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setAccessToken($accessToken)
+    public function setAccessToken(string $accessToken): static
     {
         $this->accessToken = $accessToken;
         return $this;
@@ -201,7 +203,7 @@ class Configuration
      *
      * @return string Access token for OAuth
      */
-    public function getAccessToken()
+    public function getAccessToken(): string
     {
         return $this->accessToken;
     }
@@ -209,11 +211,11 @@ class Configuration
     /**
      * Sets boolean format for query string.
      *
-     * @param string $booleanFormatForQueryString Boolean format for query string
+     * @param string $booleanFormat Boolean format for query string
      *
      * @return $this
      */
-    public function setBooleanFormatForQueryString(string $booleanFormat)
+    public function setBooleanFormatForQueryString(string $booleanFormat): static
     {
         $this->booleanFormatForQueryString = $booleanFormat;
 
@@ -237,7 +239,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setUsername($username)
+    public function setUsername(string $username): static
     {
         $this->username = $username;
         return $this;
@@ -248,7 +250,7 @@ class Configuration
      *
      * @return string Username for HTTP basic authentication
      */
-    public function getUsername()
+    public function getUsername(): string
     {
         return $this->username;
     }
@@ -260,7 +262,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setPassword($password)
+    public function setPassword(string $password): static
     {
         $this->password = $password;
         return $this;
@@ -271,7 +273,7 @@ class Configuration
      *
      * @return string Password for HTTP basic authentication
      */
-    public function getPassword()
+    public function getPassword(): string
     {
         return $this->password;
     }
@@ -283,7 +285,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setHost($host)
+    public function setHost(string $host): static
     {
         $this->host = $host;
         return $this;
@@ -294,7 +296,7 @@ class Configuration
      *
      * @return string Host
      */
-    public function getHost()
+    public function getHost(): string
     {
         return $this->host;
     }
@@ -304,15 +306,11 @@ class Configuration
      *
      * @param string $userAgent the user agent of the api client
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return $this
      */
-    public function setUserAgent($userAgent)
+    public function setUserAgent(string $userAgent): static
     {
-        if (!is_string($userAgent)) {
-            throw new \InvalidArgumentException('User-agent must be a string.');
-        }
-
         $this->userAgent = $userAgent;
         return $this;
     }
@@ -322,7 +320,7 @@ class Configuration
      *
      * @return string user agent
      */
-    public function getUserAgent()
+    public function getUserAgent(): string
     {
         return $this->userAgent;
     }
@@ -334,7 +332,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setDebug($debug)
+    public function setDebug(bool $debug): static
     {
         $this->debug = $debug;
         return $this;
@@ -345,7 +343,7 @@ class Configuration
      *
      * @return bool
      */
-    public function getDebug()
+    public function getDebug(): bool
     {
         return $this->debug;
     }
@@ -357,7 +355,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setDebugFile($debugFile)
+    public function setDebugFile(string $debugFile): static
     {
         $this->debugFile = $debugFile;
         return $this;
@@ -368,7 +366,7 @@ class Configuration
      *
      * @return string
      */
-    public function getDebugFile()
+    public function getDebugFile(): string
     {
         return $this->debugFile;
     }
@@ -380,7 +378,7 @@ class Configuration
      *
      * @return $this
      */
-    public function setTempFolderPath($tempFolderPath)
+    public function setTempFolderPath(string $tempFolderPath): static
     {
         $this->tempFolderPath = $tempFolderPath;
         return $this;
@@ -391,7 +389,7 @@ class Configuration
      *
      * @return string Temp folder path
      */
-    public function getTempFolderPath()
+    public function getTempFolderPath(): string
     {
         return $this->tempFolderPath;
     }
@@ -401,7 +399,7 @@ class Configuration
      *
      * @return Configuration
      */
-    public static function getDefaultConfiguration()
+    public static function getDefaultConfiguration(): Configuration
     {
         if (self::$defaultConfiguration === null) {
             self::$defaultConfiguration = new Configuration();
@@ -417,7 +415,7 @@ class Configuration
      *
      * @return void
      */
-    public static function setDefaultConfiguration(Configuration $config)
+    public static function setDefaultConfiguration(Configuration $config): void
     {
         self::$defaultConfiguration = $config;
     }
@@ -427,7 +425,7 @@ class Configuration
      *
      * @return string The report for debugging
      */
-    public static function toDebugReport()
+    public static function toDebugReport(): string
     {
         $report  = 'PHP SDK (OpenAPI\Client) Debug Report:' . PHP_EOL;
         $report .= '    OS: ' . php_uname() . PHP_EOL;
@@ -445,7 +443,7 @@ class Configuration
      *
      * @return null|string API key with the prefix
      */
-    public function getApiKeyWithPrefix($apiKeyIdentifier)
+    public function getApiKeyWithPrefix(string $apiKeyIdentifier): ?string
     {
         $prefix = $this->getApiKeyPrefix($apiKeyIdentifier);
         $apiKey = $this->getApiKey($apiKeyIdentifier);
@@ -468,7 +466,7 @@ class Configuration
      *
      * @return array an array of host settings
      */
-    public function getHostSettings()
+    public function getHostSettings(): array
     {
         return [
             [
@@ -481,12 +479,12 @@ class Configuration
     /**
     * Returns URL based on host settings, index and variables
     *
-    * @param array      $hostSettings array of host settings, generated from getHostSettings() or equivalent from the API clients
+    * @param array      $hostsSettings array of host settings, generated from getHostSettings() or equivalent from the API clients
     * @param int        $hostIndex    index of the host settings
     * @param array|null $variables    hash of variable and the corresponding value (optional)
     * @return string URL based on host settings
     */
-    public static function getHostString(array $hostsSettings, $hostIndex, array $variables = null)
+    public static function getHostString(array $hostsSettings, int $hostIndex, array $variables = null): string
     {
         if (null === $variables) {
             $variables = [];
@@ -494,7 +492,7 @@ class Configuration
 
         // check array index out of bound
         if ($hostIndex < 0 || $hostIndex >= count($hostsSettings)) {
-            throw new \InvalidArgumentException("Invalid index $hostIndex when selecting the host. Must be less than ".count($hostsSettings));
+            throw new InvalidArgumentException("Invalid index $hostIndex when selecting the host. Must be less than ".count($hostsSettings));
         }
 
         $host = $hostsSettings[$hostIndex];
@@ -506,7 +504,7 @@ class Configuration
                 if (!isset($variable['enum_values']) || in_array($variables[$name], $variable["enum_values"], true)) { // check to see if the value is in the enum
                     $url = str_replace("{".$name."}", $variables[$name], $url);
                 } else {
-                    throw new \InvalidArgumentException("The variable `$name` in the host URL has invalid value ".$variables[$name].". Must be ".join(',', $variable["enum_values"]).".");
+                    throw new InvalidArgumentException("The variable `$name` in the host URL has invalid value ".$variables[$name].". Must be ".join(',', $variable["enum_values"]).".");
                 }
             } else {
                 // use default value
@@ -524,7 +522,7 @@ class Configuration
      * @param array|null $variables hash of variable and the corresponding value (optional)
      * @return string URL based on host settings
      */
-    public function getHostFromSettings($index, $variables = null)
+    public function getHostFromSettings(int $index, ?array $variables = null): string
     {
         return self::getHostString($this->getHostSettings(), $index, $variables);
     }

samples/client/echo_api/php-nextgen/src/Model/Bird.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * Bird Class Doc Comment
@@ -39,9 +42,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
+class Bird implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -50,14 +53,14 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
       *
       * @var string
       */
-    protected static $openAPIModelName = 'Bird';
+    protected static string $openAPIModelName = 'Bird';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'size' => 'string',
         'color' => 'string'
     ];
@@ -65,11 +68,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'size' => null,
         'color' => null
     ];
@@ -77,7 +78,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'size' => false,
@@ -87,16 +88,16 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -104,9 +105,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -114,7 +115,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -124,7 +125,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -134,7 +135,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -167,9 +168,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'size' => 'size',
         'color' => 'color'
     ];
@@ -177,9 +178,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'size' => 'setSize',
         'color' => 'setColor'
     ];
@@ -187,9 +188,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'size' => 'getSize',
         'color' => 'getColor'
     ];
@@ -198,9 +199,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -208,9 +209,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -218,9 +219,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -230,7 +231,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -239,15 +240,14 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -264,7 +264,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -276,9 +276,9 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -291,7 +291,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -302,7 +302,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string|null
      */
-    public function getSize()
+    public function getSize(): ?string
     {
         return $this->container['size'];
     }
@@ -312,12 +312,12 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string|null $size size
      *
-     * @return self
+     * @return $this
      */
-    public function setSize($size)
+    public function setSize(?string $size): static
     {
         if (is_null($size)) {
-            throw new \InvalidArgumentException('non-nullable size cannot be null');
+            throw new InvalidArgumentException('non-nullable size cannot be null');
         }
         $this->container['size'] = $size;
 
@@ -329,7 +329,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string|null
      */
-    public function getColor()
+    public function getColor(): ?string
     {
         return $this->container['color'];
     }
@@ -339,12 +339,12 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string|null $color color
      *
-     * @return self
+     * @return $this
      */
-    public function setColor($color)
+    public function setColor(?string $color): static
     {
         if (is_null($color)) {
-            throw new \InvalidArgumentException('non-nullable color cannot be null');
+            throw new InvalidArgumentException('non-nullable color cannot be null');
         }
         $this->container['color'] = $color;
 
@@ -357,7 +357,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -369,8 +369,8 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -383,7 +383,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -399,7 +399,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -411,8 +411,8 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -422,7 +422,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -435,7 +435,7 @@ class Bird implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/Category.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * Category Class Doc Comment
@@ -39,9 +42,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class Category implements ModelInterface, ArrayAccess, \JsonSerializable
+class Category implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -50,14 +53,14 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
       *
       * @var string
       */
-    protected static $openAPIModelName = 'Category';
+    protected static string $openAPIModelName = 'Category';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'id' => 'int',
         'name' => 'string'
     ];
@@ -65,11 +68,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'id' => 'int64',
         'name' => null
     ];
@@ -77,7 +78,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'id' => false,
@@ -87,16 +88,16 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -104,9 +105,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -114,7 +115,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -124,7 +125,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -134,7 +135,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -167,9 +168,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'id' => 'id',
         'name' => 'name'
     ];
@@ -177,9 +178,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'id' => 'setId',
         'name' => 'setName'
     ];
@@ -187,9 +188,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'id' => 'getId',
         'name' => 'getName'
     ];
@@ -198,9 +199,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -208,9 +209,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -218,9 +219,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -230,7 +231,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -239,15 +240,14 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -264,7 +264,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -276,9 +276,9 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -291,7 +291,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -302,7 +302,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return int|null
      */
-    public function getId()
+    public function getId(): ?int
     {
         return $this->container['id'];
     }
@@ -312,12 +312,12 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param int|null $id id
      *
-     * @return self
+     * @return $this
      */
-    public function setId($id)
+    public function setId(?int $id): static
     {
         if (is_null($id)) {
-            throw new \InvalidArgumentException('non-nullable id cannot be null');
+            throw new InvalidArgumentException('non-nullable id cannot be null');
         }
         $this->container['id'] = $id;
 
@@ -329,7 +329,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string|null
      */
-    public function getName()
+    public function getName(): ?string
     {
         return $this->container['name'];
     }
@@ -339,12 +339,12 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string|null $name name
      *
-     * @return self
+     * @return $this
      */
-    public function setName($name)
+    public function setName(?string $name): static
     {
         if (is_null($name)) {
-            throw new \InvalidArgumentException('non-nullable name cannot be null');
+            throw new InvalidArgumentException('non-nullable name cannot be null');
         }
         $this->container['name'] = $name;
 
@@ -357,7 +357,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -369,8 +369,8 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -383,7 +383,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -399,7 +399,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -411,8 +411,8 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -422,7 +422,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -435,7 +435,7 @@ class Category implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/DataQuery.php

@@ -28,7 +28,6 @@
  */
 
 namespace OpenAPI\Client\Model;
-use \OpenAPI\Client\ObjectSerializer;
 
 /**
  * DataQuery Class Doc Comment
@@ -37,7 +36,7 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
 class DataQuery extends Query
 {
@@ -48,14 +47,14 @@ class DataQuery extends Query
       *
       * @var string
       */
-    protected static $openAPIModelName = 'DataQuery';
+    protected static string $openAPIModelName = 'DataQuery';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'suffix' => 'string',
         'text' => 'string',
         'date' => '\DateTime'
@@ -64,11 +63,9 @@ class DataQuery extends Query
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'suffix' => null,
         'text' => null,
         'date' => 'date-time'
@@ -77,7 +74,7 @@ class DataQuery extends Query
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'suffix' => false,
@@ -88,16 +85,16 @@ class DataQuery extends Query
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes + parent::openAPITypes();
     }
@@ -105,9 +102,9 @@ class DataQuery extends Query
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats + parent::openAPIFormats();
     }
@@ -115,7 +112,7 @@ class DataQuery extends Query
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -125,7 +122,7 @@ class DataQuery extends Query
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -135,7 +132,7 @@ class DataQuery extends Query
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -168,9 +165,9 @@ class DataQuery extends Query
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'suffix' => 'suffix',
         'text' => 'text',
         'date' => 'date'
@@ -179,9 +176,9 @@ class DataQuery extends Query
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'suffix' => 'setSuffix',
         'text' => 'setText',
         'date' => 'setDate'
@@ -190,9 +187,9 @@ class DataQuery extends Query
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'suffix' => 'getSuffix',
         'text' => 'getText',
         'date' => 'getDate'
@@ -202,9 +199,9 @@ class DataQuery extends Query
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return parent::attributeMap() + self::$attributeMap;
     }
@@ -212,9 +209,9 @@ class DataQuery extends Query
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return parent::setters() + self::$setters;
     }
@@ -222,9 +219,9 @@ class DataQuery extends Query
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return parent::getters() + self::$getters;
     }
@@ -234,7 +231,7 @@ class DataQuery extends Query
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -244,8 +241,7 @@ class DataQuery extends Query
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -265,7 +261,7 @@ class DataQuery extends Query
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -277,9 +273,9 @@ class DataQuery extends Query
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = parent::listInvalidProperties();
 
@@ -292,7 +288,7 @@ class DataQuery extends Query
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -303,7 +299,7 @@ class DataQuery extends Query
      *
      * @return string|null
      */
-    public function getSuffix()
+    public function getSuffix(): ?string
     {
         return $this->container['suffix'];
     }
@@ -313,12 +309,12 @@ class DataQuery extends Query
      *
      * @param string|null $suffix test suffix
      *
-     * @return self
+     * @return $this
      */
-    public function setSuffix($suffix)
+    public function setSuffix(?string $suffix): static
     {
         if (is_null($suffix)) {
-            throw new \InvalidArgumentException('non-nullable suffix cannot be null');
+            throw new InvalidArgumentException('non-nullable suffix cannot be null');
         }
         $this->container['suffix'] = $suffix;
 
@@ -330,7 +326,7 @@ class DataQuery extends Query
      *
      * @return string|null
      */
-    public function getText()
+    public function getText(): ?string
     {
         return $this->container['text'];
     }
@@ -340,12 +336,12 @@ class DataQuery extends Query
      *
      * @param string|null $text Some text containing white spaces
      *
-     * @return self
+     * @return $this
      */
-    public function setText($text)
+    public function setText(?string $text): static
     {
         if (is_null($text)) {
-            throw new \InvalidArgumentException('non-nullable text cannot be null');
+            throw new InvalidArgumentException('non-nullable text cannot be null');
         }
         $this->container['text'] = $text;
 
@@ -357,7 +353,7 @@ class DataQuery extends Query
      *
      * @return \DateTime|null
      */
-    public function getDate()
+    public function getDate(): ?\DateTime
     {
         return $this->container['date'];
     }
@@ -367,12 +363,12 @@ class DataQuery extends Query
      *
      * @param \DateTime|null $date A date
      *
-     * @return self
+     * @return $this
      */
-    public function setDate($date)
+    public function setDate(?\DateTime $date): static
     {
         if (is_null($date)) {
-            throw new \InvalidArgumentException('non-nullable date cannot be null');
+            throw new InvalidArgumentException('non-nullable date cannot be null');
         }
         $this->container['date'] = $date;
 
@@ -385,7 +381,7 @@ class DataQuery extends Query
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -397,8 +393,8 @@ class DataQuery extends Query
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -411,7 +407,7 @@ class DataQuery extends Query
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -427,7 +423,7 @@ class DataQuery extends Query
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -439,8 +435,8 @@ class DataQuery extends Query
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -450,7 +446,7 @@ class DataQuery extends Query
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -463,7 +459,7 @@ class DataQuery extends Query
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/DefaultValue.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * DefaultValue Class Doc Comment
@@ -40,9 +43,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
+class DefaultValue implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -51,14 +54,14 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
       *
       * @var string
       */
-    protected static $openAPIModelName = 'DefaultValue';
+    protected static string $openAPIModelName = 'DefaultValue';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'array_string_enum_ref_default' => '\OpenAPI\Client\Model\StringEnumRef[]',
         'array_string_enum_default' => 'string[]',
         'array_string_default' => 'string[]',
@@ -72,11 +75,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'array_string_enum_ref_default' => null,
         'array_string_enum_default' => null,
         'array_string_default' => null,
@@ -90,7 +91,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'array_string_enum_ref_default' => false,
@@ -106,16 +107,16 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -123,9 +124,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -133,7 +134,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -143,7 +144,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -153,7 +154,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -186,9 +187,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'array_string_enum_ref_default' => 'array_string_enum_ref_default',
         'array_string_enum_default' => 'array_string_enum_default',
         'array_string_default' => 'array_string_default',
@@ -202,9 +203,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'array_string_enum_ref_default' => 'setArrayStringEnumRefDefault',
         'array_string_enum_default' => 'setArrayStringEnumDefault',
         'array_string_default' => 'setArrayStringDefault',
@@ -218,9 +219,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'array_string_enum_ref_default' => 'getArrayStringEnumRefDefault',
         'array_string_enum_default' => 'getArrayStringEnumDefault',
         'array_string_default' => 'getArrayStringDefault',
@@ -235,9 +236,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -245,9 +246,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -255,9 +256,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -267,7 +268,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -293,22 +294,21 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
-        $this->setIfExists('array_string_enum_ref_default', $data ?? [], null);
-        $this->setIfExists('array_string_enum_default', $data ?? [], null);
-        $this->setIfExists('array_string_default', $data ?? [], null);
-        $this->setIfExists('array_integer_default', $data ?? [], null);
+        $this->setIfExists('array_string_enum_ref_default', $data ?? [], [["success","failure"]]);
+        $this->setIfExists('array_string_enum_default', $data ?? [], [["success","failure"]]);
+        $this->setIfExists('array_string_default', $data ?? [], [["failure","skipped"]]);
+        $this->setIfExists('array_integer_default', $data ?? [], [[1,3]]);
         $this->setIfExists('array_string', $data ?? [], null);
         $this->setIfExists('array_string_nullable', $data ?? [], null);
         $this->setIfExists('array_string_extension_nullable', $data ?? [], null);
@@ -324,7 +324,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -336,9 +336,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -351,7 +351,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -362,7 +362,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return \OpenAPI\Client\Model\StringEnumRef[]|null
      */
-    public function getArrayStringEnumRefDefault()
+    public function getArrayStringEnumRefDefault(): ?array
     {
         return $this->container['array_string_enum_ref_default'];
     }
@@ -372,12 +372,12 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param \OpenAPI\Client\Model\StringEnumRef[]|null $array_string_enum_ref_default array_string_enum_ref_default
      *
-     * @return self
+     * @return $this
      */
-    public function setArrayStringEnumRefDefault($array_string_enum_ref_default)
+    public function setArrayStringEnumRefDefault(?array $array_string_enum_ref_default): static
     {
         if (is_null($array_string_enum_ref_default)) {
-            throw new \InvalidArgumentException('non-nullable array_string_enum_ref_default cannot be null');
+            throw new InvalidArgumentException('non-nullable array_string_enum_ref_default cannot be null');
         }
         $this->container['array_string_enum_ref_default'] = $array_string_enum_ref_default;
 
@@ -389,7 +389,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string[]|null
      */
-    public function getArrayStringEnumDefault()
+    public function getArrayStringEnumDefault(): ?array
     {
         return $this->container['array_string_enum_default'];
     }
@@ -399,16 +399,16 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string[]|null $array_string_enum_default array_string_enum_default
      *
-     * @return self
+     * @return $this
      */
-    public function setArrayStringEnumDefault($array_string_enum_default)
+    public function setArrayStringEnumDefault(?array $array_string_enum_default): static
     {
         if (is_null($array_string_enum_default)) {
-            throw new \InvalidArgumentException('non-nullable array_string_enum_default cannot be null');
+            throw new InvalidArgumentException('non-nullable array_string_enum_default cannot be null');
         }
         $allowedValues = $this->getArrayStringEnumDefaultAllowableValues();
         if (array_diff($array_string_enum_default, $allowedValues)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 sprintf(
                     "Invalid value for 'array_string_enum_default', must be one of '%s'",
                     implode("', '", $allowedValues)
@@ -425,7 +425,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string[]|null
      */
-    public function getArrayStringDefault()
+    public function getArrayStringDefault(): ?array
     {
         return $this->container['array_string_default'];
     }
@@ -435,12 +435,12 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string[]|null $array_string_default array_string_default
      *
-     * @return self
+     * @return $this
      */
-    public function setArrayStringDefault($array_string_default)
+    public function setArrayStringDefault(?array $array_string_default): static
     {
         if (is_null($array_string_default)) {
-            throw new \InvalidArgumentException('non-nullable array_string_default cannot be null');
+            throw new InvalidArgumentException('non-nullable array_string_default cannot be null');
         }
         $this->container['array_string_default'] = $array_string_default;
 
@@ -452,7 +452,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return int[]|null
      */
-    public function getArrayIntegerDefault()
+    public function getArrayIntegerDefault(): ?array
     {
         return $this->container['array_integer_default'];
     }
@@ -462,12 +462,12 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param int[]|null $array_integer_default array_integer_default
      *
-     * @return self
+     * @return $this
      */
-    public function setArrayIntegerDefault($array_integer_default)
+    public function setArrayIntegerDefault(?array $array_integer_default): static
     {
         if (is_null($array_integer_default)) {
-            throw new \InvalidArgumentException('non-nullable array_integer_default cannot be null');
+            throw new InvalidArgumentException('non-nullable array_integer_default cannot be null');
         }
         $this->container['array_integer_default'] = $array_integer_default;
 
@@ -479,7 +479,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string[]|null
      */
-    public function getArrayString()
+    public function getArrayString(): ?array
     {
         return $this->container['array_string'];
     }
@@ -489,12 +489,12 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string[]|null $array_string array_string
      *
-     * @return self
+     * @return $this
      */
-    public function setArrayString($array_string)
+    public function setArrayString(?array $array_string): static
     {
         if (is_null($array_string)) {
-            throw new \InvalidArgumentException('non-nullable array_string cannot be null');
+            throw new InvalidArgumentException('non-nullable array_string cannot be null');
         }
         $this->container['array_string'] = $array_string;
 
@@ -506,7 +506,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string[]|null
      */
-    public function getArrayStringNullable()
+    public function getArrayStringNullable(): ?array
     {
         return $this->container['array_string_nullable'];
     }
@@ -516,9 +516,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string[]|null $array_string_nullable array_string_nullable
      *
-     * @return self
+     * @return $this
      */
-    public function setArrayStringNullable($array_string_nullable)
+    public function setArrayStringNullable(?array $array_string_nullable): static
     {
         if (is_null($array_string_nullable)) {
             array_push($this->openAPINullablesSetToNull, 'array_string_nullable');
@@ -540,7 +540,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string[]|null
      */
-    public function getArrayStringExtensionNullable()
+    public function getArrayStringExtensionNullable(): ?array
     {
         return $this->container['array_string_extension_nullable'];
     }
@@ -550,9 +550,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string[]|null $array_string_extension_nullable array_string_extension_nullable
      *
-     * @return self
+     * @return $this
      */
-    public function setArrayStringExtensionNullable($array_string_extension_nullable)
+    public function setArrayStringExtensionNullable(?array $array_string_extension_nullable): static
     {
         if (is_null($array_string_extension_nullable)) {
             array_push($this->openAPINullablesSetToNull, 'array_string_extension_nullable');
@@ -574,7 +574,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string|null
      */
-    public function getStringNullable()
+    public function getStringNullable(): ?string
     {
         return $this->container['string_nullable'];
     }
@@ -584,9 +584,9 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string|null $string_nullable string_nullable
      *
-     * @return self
+     * @return $this
      */
-    public function setStringNullable($string_nullable)
+    public function setStringNullable(?string $string_nullable): static
     {
         if (is_null($string_nullable)) {
             array_push($this->openAPINullablesSetToNull, 'string_nullable');
@@ -609,7 +609,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -621,8 +621,8 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -635,7 +635,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -651,7 +651,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -663,8 +663,8 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -674,7 +674,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -687,7 +687,7 @@ class DefaultValue implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/ModelInterface.php

@@ -42,49 +42,49 @@ interface ModelInterface
      *
      * @return string
      */
-    public function getModelName();
+    public function getModelName(): string;
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
      * @return array
      */
-    public static function openAPITypes();
+    public static function openAPITypes(): array;
 
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
      * @return array
      */
-    public static function openAPIFormats();
+    public static function openAPIFormats(): array;
 
     /**
      * Array of attributes where the key is the local name, and the value is the original name
      *
      * @return array
      */
-    public static function attributeMap();
+    public static function attributeMap(): array;
 
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
      * @return array
      */
-    public static function setters();
+    public static function setters(): array;
 
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
      * @return array
      */
-    public static function getters();
+    public static function getters(): array;
 
     /**
      * Show all the invalid properties with reasons.
      *
      * @return array
      */
-    public function listInvalidProperties();
+    public function listInvalidProperties(): array;
 
     /**
      * Validate all the properties in the model
@@ -92,7 +92,7 @@ interface ModelInterface
      *
      * @return bool
      */
-    public function valid();
+    public function valid(): bool;
 
     /**
      * Checks if a property is nullable

samples/client/echo_api/php-nextgen/src/Model/NumberPropertiesOnly.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * NumberPropertiesOnly Class Doc Comment
@@ -39,9 +42,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializable
+class NumberPropertiesOnly implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -50,14 +53,14 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
       *
       * @var string
       */
-    protected static $openAPIModelName = 'NumberPropertiesOnly';
+    protected static string $openAPIModelName = 'NumberPropertiesOnly';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'number' => 'float',
         'float' => 'float',
         'double' => 'float'
@@ -66,11 +69,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'number' => null,
         'float' => 'float',
         'double' => 'double'
@@ -79,7 +80,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'number' => false,
@@ -90,16 +91,16 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -107,9 +108,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -117,7 +118,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -127,7 +128,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -137,7 +138,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -170,9 +171,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'number' => 'number',
         'float' => 'float',
         'double' => 'double'
@@ -181,9 +182,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'number' => 'setNumber',
         'float' => 'setFloat',
         'double' => 'setDouble'
@@ -192,9 +193,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'number' => 'getNumber',
         'float' => 'getFloat',
         'double' => 'getDouble'
@@ -204,9 +205,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -214,9 +215,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -224,9 +225,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -236,7 +237,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -245,15 +246,14 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -271,7 +271,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -283,9 +283,9 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -306,7 +306,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -317,7 +317,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return float|null
      */
-    public function getNumber()
+    public function getNumber(): ?float
     {
         return $this->container['number'];
     }
@@ -327,12 +327,12 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @param float|null $number number
      *
-     * @return self
+     * @return $this
      */
-    public function setNumber($number)
+    public function setNumber(?float $number): static
     {
         if (is_null($number)) {
-            throw new \InvalidArgumentException('non-nullable number cannot be null');
+            throw new InvalidArgumentException('non-nullable number cannot be null');
         }
         $this->container['number'] = $number;
 
@@ -344,7 +344,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return float|null
      */
-    public function getFloat()
+    public function getFloat(): ?float
     {
         return $this->container['float'];
     }
@@ -354,12 +354,12 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @param float|null $float float
      *
-     * @return self
+     * @return $this
      */
-    public function setFloat($float)
+    public function setFloat(?float $float): static
     {
         if (is_null($float)) {
-            throw new \InvalidArgumentException('non-nullable float cannot be null');
+            throw new InvalidArgumentException('non-nullable float cannot be null');
         }
         $this->container['float'] = $float;
 
@@ -371,7 +371,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return float|null
      */
-    public function getDouble()
+    public function getDouble(): ?float
     {
         return $this->container['double'];
     }
@@ -381,19 +381,19 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @param float|null $double double
      *
-     * @return self
+     * @return $this
      */
-    public function setDouble($double)
+    public function setDouble(?float $double): static
     {
         if (is_null($double)) {
-            throw new \InvalidArgumentException('non-nullable double cannot be null');
+            throw new InvalidArgumentException('non-nullable double cannot be null');
         }
 
         if (($double > 50.2)) {
-            throw new \InvalidArgumentException('invalid value for $double when calling NumberPropertiesOnly., must be smaller than or equal to 50.2.');
+            throw new InvalidArgumentException('invalid value for $double when calling NumberPropertiesOnly., must be smaller than or equal to 50.2.');
         }
         if (($double < 0.8)) {
-            throw new \InvalidArgumentException('invalid value for $double when calling NumberPropertiesOnly., must be bigger than or equal to 0.8.');
+            throw new InvalidArgumentException('invalid value for $double when calling NumberPropertiesOnly., must be bigger than or equal to 0.8.');
         }
 
         $this->container['double'] = $double;
@@ -407,7 +407,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -419,8 +419,8 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -433,7 +433,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -449,7 +449,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -461,8 +461,8 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -472,7 +472,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -485,7 +485,7 @@ class NumberPropertiesOnly implements ModelInterface, ArrayAccess, \JsonSerializ
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/Pet.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * Pet Class Doc Comment
@@ -39,9 +42,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
+class Pet implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -50,14 +53,14 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
       *
       * @var string
       */
-    protected static $openAPIModelName = 'Pet';
+    protected static string $openAPIModelName = 'Pet';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'id' => 'int',
         'name' => 'string',
         'category' => '\OpenAPI\Client\Model\Category',
@@ -69,11 +72,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'id' => 'int64',
         'name' => null,
         'category' => null,
@@ -85,7 +86,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'id' => false,
@@ -99,16 +100,16 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -116,9 +117,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -126,7 +127,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -136,7 +137,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -146,7 +147,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -179,9 +180,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'id' => 'id',
         'name' => 'name',
         'category' => 'category',
@@ -193,9 +194,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'id' => 'setId',
         'name' => 'setName',
         'category' => 'setCategory',
@@ -207,9 +208,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'id' => 'getId',
         'name' => 'getName',
         'category' => 'getCategory',
@@ -222,9 +223,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -232,9 +233,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -242,9 +243,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -254,7 +255,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -280,15 +281,14 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -309,7 +309,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -321,9 +321,9 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -351,7 +351,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -362,7 +362,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return int|null
      */
-    public function getId()
+    public function getId(): ?int
     {
         return $this->container['id'];
     }
@@ -372,12 +372,12 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param int|null $id id
      *
-     * @return self
+     * @return $this
      */
-    public function setId($id)
+    public function setId(?int $id): static
     {
         if (is_null($id)) {
-            throw new \InvalidArgumentException('non-nullable id cannot be null');
+            throw new InvalidArgumentException('non-nullable id cannot be null');
         }
         $this->container['id'] = $id;
 
@@ -389,7 +389,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function getName()
+    public function getName(): string
     {
         return $this->container['name'];
     }
@@ -399,12 +399,12 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string $name name
      *
-     * @return self
+     * @return $this
      */
-    public function setName($name)
+    public function setName(string $name): static
     {
         if (is_null($name)) {
-            throw new \InvalidArgumentException('non-nullable name cannot be null');
+            throw new InvalidArgumentException('non-nullable name cannot be null');
         }
         $this->container['name'] = $name;
 
@@ -416,7 +416,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return \OpenAPI\Client\Model\Category|null
      */
-    public function getCategory()
+    public function getCategory(): ?\OpenAPI\Client\Model\Category
     {
         return $this->container['category'];
     }
@@ -426,12 +426,12 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param \OpenAPI\Client\Model\Category|null $category category
      *
-     * @return self
+     * @return $this
      */
-    public function setCategory($category)
+    public function setCategory(?\OpenAPI\Client\Model\Category $category): static
     {
         if (is_null($category)) {
-            throw new \InvalidArgumentException('non-nullable category cannot be null');
+            throw new InvalidArgumentException('non-nullable category cannot be null');
         }
         $this->container['category'] = $category;
 
@@ -443,7 +443,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string[]
      */
-    public function getPhotoUrls()
+    public function getPhotoUrls(): array
     {
         return $this->container['photo_urls'];
     }
@@ -453,12 +453,12 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string[] $photo_urls photo_urls
      *
-     * @return self
+     * @return $this
      */
-    public function setPhotoUrls($photo_urls)
+    public function setPhotoUrls(array $photo_urls): static
     {
         if (is_null($photo_urls)) {
-            throw new \InvalidArgumentException('non-nullable photo_urls cannot be null');
+            throw new InvalidArgumentException('non-nullable photo_urls cannot be null');
         }
         $this->container['photo_urls'] = $photo_urls;
 
@@ -470,7 +470,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return \OpenAPI\Client\Model\Tag[]|null
      */
-    public function getTags()
+    public function getTags(): ?array
     {
         return $this->container['tags'];
     }
@@ -480,12 +480,12 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param \OpenAPI\Client\Model\Tag[]|null $tags tags
      *
-     * @return self
+     * @return $this
      */
-    public function setTags($tags)
+    public function setTags(?array $tags): static
     {
         if (is_null($tags)) {
-            throw new \InvalidArgumentException('non-nullable tags cannot be null');
+            throw new InvalidArgumentException('non-nullable tags cannot be null');
         }
         $this->container['tags'] = $tags;
 
@@ -497,7 +497,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string|null
      */
-    public function getStatus()
+    public function getStatus(): ?string
     {
         return $this->container['status'];
     }
@@ -507,16 +507,16 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string|null $status pet status in the store
      *
-     * @return self
+     * @return $this
      */
-    public function setStatus($status)
+    public function setStatus(?string $status): static
     {
         if (is_null($status)) {
-            throw new \InvalidArgumentException('non-nullable status cannot be null');
+            throw new InvalidArgumentException('non-nullable status cannot be null');
         }
         $allowedValues = $this->getStatusAllowableValues();
         if (!in_array($status, $allowedValues, true)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 sprintf(
                     "Invalid value '%s' for 'status', must be one of '%s'",
                     $status,
@@ -535,7 +535,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -547,8 +547,8 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -561,7 +561,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -577,7 +577,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -589,8 +589,8 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -600,7 +600,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -613,7 +613,7 @@ class Pet implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/Query.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * Query Class Doc Comment
@@ -39,9 +42,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class Query implements ModelInterface, ArrayAccess, \JsonSerializable
+class Query implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -50,14 +53,14 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
       *
       * @var string
       */
-    protected static $openAPIModelName = 'Query';
+    protected static string $openAPIModelName = 'Query';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'id' => 'int',
         'outcomes' => 'string[]'
     ];
@@ -65,11 +68,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'id' => 'int64',
         'outcomes' => null
     ];
@@ -77,7 +78,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'id' => false,
@@ -87,16 +88,16 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -104,9 +105,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -114,7 +115,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -124,7 +125,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -134,7 +135,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -167,9 +168,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'id' => 'id',
         'outcomes' => 'outcomes'
     ];
@@ -177,9 +178,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'id' => 'setId',
         'outcomes' => 'setOutcomes'
     ];
@@ -187,9 +188,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'id' => 'getId',
         'outcomes' => 'getOutcomes'
     ];
@@ -198,9 +199,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -208,9 +209,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -218,9 +219,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -230,7 +231,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -256,20 +257,19 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
         $this->setIfExists('id', $data ?? [], null);
-        $this->setIfExists('outcomes', $data ?? [], null);
+        $this->setIfExists('outcomes', $data ?? [], [["SUCCESS","FAILURE"]]);
     }
 
     /**
@@ -281,7 +281,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -293,9 +293,9 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -308,7 +308,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -319,7 +319,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return int|null
      */
-    public function getId()
+    public function getId(): ?int
     {
         return $this->container['id'];
     }
@@ -329,12 +329,12 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param int|null $id Query
      *
-     * @return self
+     * @return $this
      */
-    public function setId($id)
+    public function setId(?int $id): static
     {
         if (is_null($id)) {
-            throw new \InvalidArgumentException('non-nullable id cannot be null');
+            throw new InvalidArgumentException('non-nullable id cannot be null');
         }
         $this->container['id'] = $id;
 
@@ -346,7 +346,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string[]|null
      */
-    public function getOutcomes()
+    public function getOutcomes(): ?array
     {
         return $this->container['outcomes'];
     }
@@ -356,16 +356,16 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string[]|null $outcomes outcomes
      *
-     * @return self
+     * @return $this
      */
-    public function setOutcomes($outcomes)
+    public function setOutcomes(?array $outcomes): static
     {
         if (is_null($outcomes)) {
-            throw new \InvalidArgumentException('non-nullable outcomes cannot be null');
+            throw new InvalidArgumentException('non-nullable outcomes cannot be null');
         }
         $allowedValues = $this->getOutcomesAllowableValues();
         if (array_diff($outcomes, $allowedValues)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 sprintf(
                     "Invalid value for 'outcomes', must be one of '%s'",
                     implode("', '", $allowedValues)
@@ -383,7 +383,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -395,8 +395,8 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -409,7 +409,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -425,7 +425,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -437,8 +437,8 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -448,7 +448,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -461,7 +461,7 @@ class Query implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/StringEnumRef.php

@@ -28,7 +28,6 @@
  */
 
 namespace OpenAPI\Client\Model;
-use \OpenAPI\Client\ObjectSerializer;
 
 /**
  * StringEnumRef Class Doc Comment

samples/client/echo_api/php-nextgen/src/Model/Tag.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * Tag Class Doc Comment
@@ -39,9 +42,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
+class Tag implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -50,14 +53,14 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
       *
       * @var string
       */
-    protected static $openAPIModelName = 'Tag';
+    protected static string $openAPIModelName = 'Tag';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'id' => 'int',
         'name' => 'string'
     ];
@@ -65,11 +68,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'id' => 'int64',
         'name' => null
     ];
@@ -77,7 +78,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'id' => false,
@@ -87,16 +88,16 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -104,9 +105,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -114,7 +115,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -124,7 +125,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -134,7 +135,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -167,9 +168,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'id' => 'id',
         'name' => 'name'
     ];
@@ -177,9 +178,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'id' => 'setId',
         'name' => 'setName'
     ];
@@ -187,9 +188,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'id' => 'getId',
         'name' => 'getName'
     ];
@@ -198,9 +199,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -208,9 +209,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -218,9 +219,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -230,7 +231,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -239,15 +240,14 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -264,7 +264,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -276,9 +276,9 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -291,7 +291,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -302,7 +302,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return int|null
      */
-    public function getId()
+    public function getId(): ?int
     {
         return $this->container['id'];
     }
@@ -312,12 +312,12 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param int|null $id id
      *
-     * @return self
+     * @return $this
      */
-    public function setId($id)
+    public function setId(?int $id): static
     {
         if (is_null($id)) {
-            throw new \InvalidArgumentException('non-nullable id cannot be null');
+            throw new InvalidArgumentException('non-nullable id cannot be null');
         }
         $this->container['id'] = $id;
 
@@ -329,7 +329,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string|null
      */
-    public function getName()
+    public function getName(): ?string
     {
         return $this->container['name'];
     }
@@ -339,12 +339,12 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @param string|null $name name
      *
-     * @return self
+     * @return $this
      */
-    public function setName($name)
+    public function setName(?string $name): static
     {
         if (is_null($name)) {
-            throw new \InvalidArgumentException('non-nullable name cannot be null');
+            throw new InvalidArgumentException('non-nullable name cannot be null');
         }
         $this->container['name'] = $name;
 
@@ -357,7 +357,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -369,8 +369,8 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -383,7 +383,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -399,7 +399,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -411,8 +411,8 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -422,7 +422,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -435,7 +435,7 @@ class Tag implements ModelInterface, ArrayAccess, \JsonSerializable
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter Class Doc Comment
@@ -39,9 +42,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter implements ModelInterface, ArrayAccess, \JsonSerializable
+class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -50,14 +53,14 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
       *
       * @var string
       */
-    protected static $openAPIModelName = 'test_query_style_deepObject_explode_true_object_allOf_query_object_parameter';
+    protected static string $openAPIModelName = 'test_query_style_deepObject_explode_true_object_allOf_query_object_parameter';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'size' => 'string',
         'color' => 'string',
         'id' => 'int',
@@ -67,11 +70,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'size' => null,
         'color' => null,
         'id' => 'int64',
@@ -81,7 +82,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'size' => false,
@@ -93,16 +94,16 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -110,9 +111,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -120,7 +121,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -130,7 +131,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -140,7 +141,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -173,9 +174,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'size' => 'size',
         'color' => 'color',
         'id' => 'id',
@@ -185,9 +186,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'size' => 'setSize',
         'color' => 'setColor',
         'id' => 'setId',
@@ -197,9 +198,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'size' => 'getSize',
         'color' => 'getColor',
         'id' => 'getId',
@@ -210,9 +211,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -220,9 +221,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -230,9 +231,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -242,7 +243,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -251,15 +252,14 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -278,7 +278,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -290,9 +290,9 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -305,7 +305,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -316,7 +316,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return string|null
      */
-    public function getSize()
+    public function getSize(): ?string
     {
         return $this->container['size'];
     }
@@ -326,12 +326,12 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @param string|null $size size
      *
-     * @return self
+     * @return $this
      */
-    public function setSize($size)
+    public function setSize(?string $size): static
     {
         if (is_null($size)) {
-            throw new \InvalidArgumentException('non-nullable size cannot be null');
+            throw new InvalidArgumentException('non-nullable size cannot be null');
         }
         $this->container['size'] = $size;
 
@@ -343,7 +343,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return string|null
      */
-    public function getColor()
+    public function getColor(): ?string
     {
         return $this->container['color'];
     }
@@ -353,12 +353,12 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @param string|null $color color
      *
-     * @return self
+     * @return $this
      */
-    public function setColor($color)
+    public function setColor(?string $color): static
     {
         if (is_null($color)) {
-            throw new \InvalidArgumentException('non-nullable color cannot be null');
+            throw new InvalidArgumentException('non-nullable color cannot be null');
         }
         $this->container['color'] = $color;
 
@@ -370,7 +370,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return int|null
      */
-    public function getId()
+    public function getId(): ?int
     {
         return $this->container['id'];
     }
@@ -380,12 +380,12 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @param int|null $id id
      *
-     * @return self
+     * @return $this
      */
-    public function setId($id)
+    public function setId(?int $id): static
     {
         if (is_null($id)) {
-            throw new \InvalidArgumentException('non-nullable id cannot be null');
+            throw new InvalidArgumentException('non-nullable id cannot be null');
         }
         $this->container['id'] = $id;
 
@@ -397,7 +397,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return string|null
      */
-    public function getName()
+    public function getName(): ?string
     {
         return $this->container['name'];
     }
@@ -407,12 +407,12 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @param string|null $name name
      *
-     * @return self
+     * @return $this
      */
-    public function setName($name)
+    public function setName(?string $name): static
     {
         if (is_null($name)) {
-            throw new \InvalidArgumentException('non-nullable name cannot be null');
+            throw new InvalidArgumentException('non-nullable name cannot be null');
         }
         $this->container['name'] = $name;
 
@@ -425,7 +425,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -437,8 +437,8 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -451,7 +451,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -467,7 +467,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -479,8 +479,8 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -490,7 +490,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -503,7 +503,7 @@ class TestQueryStyleDeepObjectExplodeTrueObjectAllOfQueryObjectParameter impleme
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/Model/TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter.php

@@ -29,8 +29,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter Class Doc Comment
@@ -39,9 +42,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements ModelInterface, ArrayAccess, \JsonSerializable
+class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -50,32 +53,30 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
       *
       * @var string
       */
-    protected static $openAPIModelName = 'test_query_style_form_explode_true_array_string_query_object_parameter';
+    protected static string $openAPIModelName = 'test_query_style_form_explode_true_array_string_query_object_parameter';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'values' => 'string[]'
     ];
 
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'values' => null
     ];
 
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'values' => false
@@ -84,16 +85,16 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -101,9 +102,9 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -111,7 +112,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -121,7 +122,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -131,7 +132,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -164,27 +165,27 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'values' => 'values'
     ];
 
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'values' => 'setValues'
     ];
 
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'values' => 'getValues'
     ];
 
@@ -192,9 +193,9 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -202,9 +203,9 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -212,9 +213,9 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -224,7 +225,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -233,15 +234,14 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -257,7 +257,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -269,9 +269,9 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -284,7 +284,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -295,7 +295,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return string[]|null
      */
-    public function getValues()
+    public function getValues(): ?array
     {
         return $this->container['values'];
     }
@@ -305,12 +305,12 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @param string[]|null $values values
      *
-     * @return self
+     * @return $this
      */
-    public function setValues($values)
+    public function setValues(?array $values): static
     {
         if (is_null($values)) {
-            throw new \InvalidArgumentException('non-nullable values cannot be null');
+            throw new InvalidArgumentException('non-nullable values cannot be null');
         }
         $this->container['values'] = $values;
 
@@ -323,7 +323,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -335,8 +335,8 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -349,7 +349,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -365,7 +365,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -377,8 +377,8 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -388,7 +388,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -401,7 +401,7 @@ class TestQueryStyleFormExplodeTrueArrayStringQueryObjectParameter implements Mo
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/echo_api/php-nextgen/src/ObjectSerializer.php

@@ -29,6 +29,8 @@
 
 namespace OpenAPI\Client;
 
+use DateTimeInterface;
+use DateTime;
 use GuzzleHttp\Psr7\Utils;
 use OpenAPI\Client\Model\ModelInterface;
 
@@ -43,14 +45,16 @@ use OpenAPI\Client\Model\ModelInterface;
 class ObjectSerializer
 {
     /** @var string */
-    private static $dateTimeFormat = \DateTime::ATOM;
+    private static string $dateTimeFormat = DateTimeInterface::ATOM;
 
     /**
      * Change the date format
      *
      * @param string $format   the new date format to use
+     *
+     * @return void
      */
-    public static function setDateTimeFormat($format)
+    public static function setDateTimeFormat(string $format): void
     {
         self::$dateTimeFormat = $format;
     }
@@ -59,18 +63,18 @@ class ObjectSerializer
      * Serialize data
      *
      * @param mixed       $data   the data to serialize
-     * @param string $type   the OpenAPIToolsType of the data
-     * @param string $format the format of the OpenAPITools type of the data
+     * @param string|null $type   the OpenAPIToolsType of the data
+     * @param string|null $format the format of the OpenAPITools type of the data
      *
      * @return scalar|object|array|null serialized form of $data
      */
-    public static function sanitizeForSerialization($data, $type = null, $format = null)
+    public static function sanitizeForSerialization(mixed $data, string $type = null, string $format = null): mixed
     {
         if (is_scalar($data) || null === $data) {
             return $data;
         }
 
-        if ($data instanceof \DateTime) {
+        if ($data instanceof DateTime) {
             return ($format === 'date') ? $data->format('Y-m-d') : $data->format(self::$dateTimeFormat);
         }
 
@@ -120,7 +124,7 @@ class ObjectSerializer
      *
      * @return string the sanitized filename
      */
-    public static function sanitizeFilename($filename)
+    public static function sanitizeFilename(string $filename): string
     {
         if (preg_match("/.*[\/\\\\](.*)$/", $filename, $match)) {
             return $match[1];
@@ -136,10 +140,8 @@ class ObjectSerializer
      *
      * @return string the shorten timestamp
      */
-    public static function sanitizeTimestamp($timestamp)
+    public static function sanitizeTimestamp(string $timestamp): string
     {
-        if (!is_string($timestamp)) return $timestamp;
-
         return preg_replace('/(:\d{2}.\d{6})\d*/', '$1', $timestamp);
     }
 
@@ -151,7 +153,7 @@ class ObjectSerializer
      *
      * @return string the serialized object
      */
-    public static function toPathValue($value)
+    public static function toPathValue(string $value): string
     {
         return rawurlencode(self::toString($value));
     }
@@ -164,7 +166,7 @@ class ObjectSerializer
      *
      * @return bool true if $value is empty
      */
-    private static function isEmptyValue($value, string $openApiType): bool
+    private static function isEmptyValue(mixed $value, string $openApiType): bool
     {
         # If empty() returns false, it is not empty regardless of its type.
         if (!empty($value)) {
@@ -176,27 +178,19 @@ class ObjectSerializer
             return true;
         }
 
-        switch ($openApiType) {
+        return match ($openApiType) {
             # For numeric values, false and '' are considered empty.
             # This comparison is safe for floating point values, since the previous call to empty() will
             # filter out values that don't match 0.
-            case 'int':
-            case 'integer':
-                return $value !== 0;
-
-            case 'number':
-            case 'float':
-                return $value !== 0 && $value !== 0.0;
+            'int','integer' => $value !== 0,
+            'number'|'float' => $value !== 0 && $value !== 0.0,
 
             # For boolean values, '' is considered empty
-            case 'bool':
-            case 'boolean':
-                return !in_array($value, [false, 0], true);
+            'bool','boolean' => !in_array($value, [false, 0], true),
 
             # For all the other types, any value at this point can be considered empty.
-            default:
-                return true;
-        }
+            default => true
+        };
     }
 
     /**
@@ -205,7 +199,7 @@ class ObjectSerializer
      *
      * @param mixed  $value       Parameter value
      * @param string $paramName   Parameter name
-     * @param string $openApiType OpenAPIType eg. array or object
+     * @param string $openApiType OpenAPIType e.g. array or object
      * @param string $style       Parameter serialization style
      * @param bool   $explode     Parameter explode option
      * @param bool   $required    Whether query param is required or not
@@ -213,7 +207,7 @@ class ObjectSerializer
      * @return array
      */
     public static function toQueryValue(
-        $value,
+        mixed $value,
         string $paramName,
         string $openApiType = 'string',
         string $style = 'form',
@@ -234,7 +228,7 @@ class ObjectSerializer
         }
 
         # Handle DateTime objects in query
-        if($openApiType === "\\DateTime" && $value instanceof \DateTime) {
+        if($openApiType === "\DateTime" && $value instanceof DateTime) {
             return ["{$paramName}" => $value->format(self::$dateTimeFormat)];
         }
 
@@ -247,7 +241,7 @@ class ObjectSerializer
             if (!is_array($arr)) return $arr;
 
             foreach ($arr as $k => $v) {
-                $prop = ($style === 'deepObject') ? $prop = "{$name}[{$k}]" : $k;
+                $prop = ($style === 'deepObject') ? "{$name}[{$k}]" : $k;
 
                 if (is_array($v)) {
                     $flattenArray($v, $prop, $result);
@@ -285,7 +279,7 @@ class ObjectSerializer
      *
      * @return int|string Boolean value in format
      */
-    public static function convertBoolToQueryStringFormat(bool $value)
+    public static function convertBoolToQueryStringFormat(bool $value): int|string
     {
         if (Configuration::BOOLEAN_FORMAT_STRING == Configuration::getDefaultConfiguration()->getBooleanFormatForQueryString()) {
             return $value ? 'true' : 'false';
@@ -303,7 +297,7 @@ class ObjectSerializer
      *
      * @return string the header string
      */
-    public static function toHeaderValue($value)
+    public static function toHeaderValue(string $value): string
     {
         $callable = [$value, 'toHeaderValue'];
         if (is_callable($callable)) {
@@ -322,7 +316,7 @@ class ObjectSerializer
      *
      * @return string the form string
      */
-    public static function toFormValue($value)
+    public static function toFormValue(string|\SplFileObject $value): string
     {
         if ($value instanceof \SplFileObject) {
             return $value->getRealPath();
@@ -337,13 +331,13 @@ class ObjectSerializer
      * If it's a datetime object, format it in ISO8601
      * If it's a boolean, convert it to "true" or "false".
      *
-     * @param string|bool|\DateTime $value the value of the parameter
+     * @param string|bool|DateTime $value the value of the parameter
      *
      * @return string the header string
      */
-    public static function toString($value)
+    public static function toString(string|bool|DateTime $value): string
     {
-        if ($value instanceof \DateTime) { // datetime in ISO8601 format
+        if ($value instanceof DateTime) { // datetime in ISO8601 format
             return $value->format(self::$dateTimeFormat);
         } elseif (is_bool($value)) {
             return $value ? 'true' : 'false';
@@ -362,31 +356,19 @@ class ObjectSerializer
      *
      * @return string
      */
-    public static function serializeCollection(array $collection, $style, $allowCollectionFormatMulti = false)
+    public static function serializeCollection(array $collection, string $style, bool $allowCollectionFormatMulti = false): string
     {
         if ($allowCollectionFormatMulti && ('multi' === $style)) {
             // http_build_query() almost does the job for us. We just
             // need to fix the result of multidimensional arrays.
             return preg_replace('/%5B[0-9]+%5D=/', '=', http_build_query($collection, '', '&'));
         }
-        switch ($style) {
-            case 'pipeDelimited':
-            case 'pipes':
-                return implode('|', $collection);
-
-            case 'tsv':
-                return implode("\t", $collection);
-
-            case 'spaceDelimited':
-            case 'ssv':
-                return implode(' ', $collection);
-
-            case 'simple':
-            case 'csv':
-                // Deliberate fall through. CSV is default format.
-            default:
-                return implode(',', $collection);
-        }
+        return match ($style) {
+            'pipeDelimited', 'pipes' => implode('|', $collection),
+            'tsv' => implode("\t", $collection),
+            'spaceDelimited', 'ssv' => implode(' ', $collection),
+            default => implode(',', $collection),
+        };
     }
 
     /**
@@ -394,12 +376,12 @@ class ObjectSerializer
      *
      * @param mixed         $data          object or primitive to be deserialized
      * @param string        $class         class name is passed as a string
-     * @param string[] $httpHeaders   HTTP headers
-     * @param string   $discriminator discriminator if polymorphism is used
+     * @param string[]|null $httpHeaders   HTTP headers
+     * @param string|null   $discriminator discriminator if polymorphism is used
      *
      * @return object|array|null a single or an array of $class instances
      */
-    public static function deserialize($data, $class, $httpHeaders = null)
+    public static function deserialize(mixed $data, string $class, string $httpHeaders = null): object|array|null
     {
         if (null === $data) {
             return null;
@@ -443,7 +425,7 @@ class ObjectSerializer
             return $data;
         }
 
-        if ($class === '\DateTime') {
+        if ($class === 'DateTime') {
             // Some APIs return an invalid, empty string as a
             // date-time property. DateTime::__construct() will return
             // the current time for empty input which is probably not
@@ -452,12 +434,12 @@ class ObjectSerializer
             // this graceful.
             if (!empty($data)) {
                 try {
-                    return new \DateTime($data);
+                    return new DateTime($data);
                 } catch (\Exception $exception) {
                     // Some APIs return a date-time with too high nanosecond
                     // precision for php's DateTime to handle.
                     // With provided regexp 6 digits of microseconds saved
-                    return new \DateTime(self::sanitizeTimestamp($data));
+                    return new DateTime(self::sanitizeTimestamp($data));
                 }
             } else {
                 return null;
@@ -557,7 +539,7 @@ class ObjectSerializer
      * @return string
      */
     public static function buildQuery(
-        $data,
+        array|object $data,
         string       $numeric_prefix = '',
         ?string      $arg_separator = null,
         int          $encoding_type = \PHP_QUERY_RFC3986

samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Api/FakeApi.php

@@ -4923,11 +4923,14 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\TestInlineFreeformAdditionalPropertiesRequest $test_inline_freeform_additional_properties_request request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testInlineFreeformAdditionalProperties'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return void
      */
-    public function testInlineFreeformAdditionalProperties($test_inline_freeform_additional_properties_request, string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0])
+    public function testInlineFreeformAdditionalProperties(
+        \OpenAPI\Client\Model\TestInlineFreeformAdditionalPropertiesRequest $test_inline_freeform_additional_properties_request,
+        string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0]
+    ): void
     {
         $this->testInlineFreeformAdditionalPropertiesWithHttpInfo($test_inline_freeform_additional_properties_request, $contentType);
     }
@@ -4940,11 +4943,14 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\TestInlineFreeformAdditionalPropertiesRequest $test_inline_freeform_additional_properties_request request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testInlineFreeformAdditionalProperties'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of null, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testInlineFreeformAdditionalPropertiesWithHttpInfo($test_inline_freeform_additional_properties_request, string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0])
+    public function testInlineFreeformAdditionalPropertiesWithHttpInfo(
+        \OpenAPI\Client\Model\TestInlineFreeformAdditionalPropertiesRequest $test_inline_freeform_additional_properties_request,
+        string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0]
+    ): array
     {
         $request = $this->testInlineFreeformAdditionalPropertiesRequest($test_inline_freeform_additional_properties_request, $contentType);
 
@@ -5000,10 +5006,13 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\TestInlineFreeformAdditionalPropertiesRequest $test_inline_freeform_additional_properties_request request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testInlineFreeformAdditionalProperties'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testInlineFreeformAdditionalPropertiesAsync($test_inline_freeform_additional_properties_request, string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0])
+    public function testInlineFreeformAdditionalPropertiesAsync(
+        \OpenAPI\Client\Model\TestInlineFreeformAdditionalPropertiesRequest $test_inline_freeform_additional_properties_request,
+        string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0]
+    ): PromiseInterface
     {
         return $this->testInlineFreeformAdditionalPropertiesAsyncWithHttpInfo($test_inline_freeform_additional_properties_request, $contentType)
             ->then(
@@ -5021,10 +5030,13 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\TestInlineFreeformAdditionalPropertiesRequest $test_inline_freeform_additional_properties_request request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testInlineFreeformAdditionalProperties'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testInlineFreeformAdditionalPropertiesAsyncWithHttpInfo($test_inline_freeform_additional_properties_request, string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0])
+    public function testInlineFreeformAdditionalPropertiesAsyncWithHttpInfo(
+        $test_inline_freeform_additional_properties_request,
+        string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0]
+    ): PromiseInterface
     {
         $returnType = '';
         $request = $this->testInlineFreeformAdditionalPropertiesRequest($test_inline_freeform_additional_properties_request, $contentType);
@@ -5058,15 +5070,18 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\TestInlineFreeformAdditionalPropertiesRequest $test_inline_freeform_additional_properties_request request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testInlineFreeformAdditionalProperties'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testInlineFreeformAdditionalPropertiesRequest($test_inline_freeform_additional_properties_request, string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0])
+    public function testInlineFreeformAdditionalPropertiesRequest(
+        $test_inline_freeform_additional_properties_request,
+        string $contentType = self::contentTypes['testInlineFreeformAdditionalProperties'][0]
+    ): Request
     {
 
         // verify the required parameter 'test_inline_freeform_additional_properties_request' is set
         if ($test_inline_freeform_additional_properties_request === null || (is_array($test_inline_freeform_additional_properties_request) && count($test_inline_freeform_additional_properties_request) === 0)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 'Missing the required parameter $test_inline_freeform_additional_properties_request when calling testInlineFreeformAdditionalProperties'
             );
         }
@@ -5412,11 +5427,14 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\ChildWithNullable $child_with_nullable request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testNullable'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return void
      */
-    public function testNullable($child_with_nullable, string $contentType = self::contentTypes['testNullable'][0])
+    public function testNullable(
+        \OpenAPI\Client\Model\ChildWithNullable $child_with_nullable,
+        string $contentType = self::contentTypes['testNullable'][0]
+    ): void
     {
         $this->testNullableWithHttpInfo($child_with_nullable, $contentType);
     }
@@ -5429,11 +5447,14 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\ChildWithNullable $child_with_nullable request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testNullable'] to see the possible values for this operation
      *
-     * @throws \OpenAPI\Client\ApiException on non-2xx response
-     * @throws \InvalidArgumentException
+     * @throws ApiException on non-2xx response
+     * @throws InvalidArgumentException
      * @return array of null, HTTP status code, HTTP response headers (array of strings)
      */
-    public function testNullableWithHttpInfo($child_with_nullable, string $contentType = self::contentTypes['testNullable'][0])
+    public function testNullableWithHttpInfo(
+        \OpenAPI\Client\Model\ChildWithNullable $child_with_nullable,
+        string $contentType = self::contentTypes['testNullable'][0]
+    ): array
     {
         $request = $this->testNullableRequest($child_with_nullable, $contentType);
 
@@ -5489,10 +5510,13 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\ChildWithNullable $child_with_nullable request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testNullable'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testNullableAsync($child_with_nullable, string $contentType = self::contentTypes['testNullable'][0])
+    public function testNullableAsync(
+        \OpenAPI\Client\Model\ChildWithNullable $child_with_nullable,
+        string $contentType = self::contentTypes['testNullable'][0]
+    ): PromiseInterface
     {
         return $this->testNullableAsyncWithHttpInfo($child_with_nullable, $contentType)
             ->then(
@@ -5510,10 +5534,13 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\ChildWithNullable $child_with_nullable request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testNullable'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
-     * @return \GuzzleHttp\Promise\PromiseInterface
+     * @throws InvalidArgumentException
+     * @return PromiseInterface
      */
-    public function testNullableAsyncWithHttpInfo($child_with_nullable, string $contentType = self::contentTypes['testNullable'][0])
+    public function testNullableAsyncWithHttpInfo(
+        $child_with_nullable,
+        string $contentType = self::contentTypes['testNullable'][0]
+    ): PromiseInterface
     {
         $returnType = '';
         $request = $this->testNullableRequest($child_with_nullable, $contentType);
@@ -5547,15 +5574,18 @@ class FakeApi
      * @param  \OpenAPI\Client\Model\ChildWithNullable $child_with_nullable request body (required)
      * @param  string $contentType The value for the Content-Type header. Check self::contentTypes['testNullable'] to see the possible values for this operation
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return \GuzzleHttp\Psr7\Request
      */
-    public function testNullableRequest($child_with_nullable, string $contentType = self::contentTypes['testNullable'][0])
+    public function testNullableRequest(
+        $child_with_nullable,
+        string $contentType = self::contentTypes['testNullable'][0]
+    ): Request
     {
 
         // verify the required parameter 'child_with_nullable' is set
         if ($child_with_nullable === null || (is_array($child_with_nullable) && count($child_with_nullable) === 0)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 'Missing the required parameter $child_with_nullable when calling testNullable'
             );
         }

samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/ChildWithNullable.php

@@ -27,7 +27,6 @@
  */
 
 namespace OpenAPI\Client\Model;
-use \OpenAPI\Client\ObjectSerializer;
 
 /**
  * ChildWithNullable Class Doc Comment
@@ -36,7 +35,7 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
 class ChildWithNullable extends ParentWithNullable
 {
@@ -47,32 +46,30 @@ class ChildWithNullable extends ParentWithNullable
       *
       * @var string
       */
-    protected static $openAPIModelName = 'ChildWithNullable';
+    protected static string $openAPIModelName = 'ChildWithNullable';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'other_property' => 'string'
     ];
 
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'other_property' => null
     ];
 
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'other_property' => false
@@ -81,16 +78,16 @@ class ChildWithNullable extends ParentWithNullable
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes + parent::openAPITypes();
     }
@@ -98,9 +95,9 @@ class ChildWithNullable extends ParentWithNullable
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats + parent::openAPIFormats();
     }
@@ -108,7 +105,7 @@ class ChildWithNullable extends ParentWithNullable
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -118,7 +115,7 @@ class ChildWithNullable extends ParentWithNullable
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -128,7 +125,7 @@ class ChildWithNullable extends ParentWithNullable
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -161,27 +158,27 @@ class ChildWithNullable extends ParentWithNullable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'other_property' => 'otherProperty'
     ];
 
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'other_property' => 'setOtherProperty'
     ];
 
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'other_property' => 'getOtherProperty'
     ];
 
@@ -189,9 +186,9 @@ class ChildWithNullable extends ParentWithNullable
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return parent::attributeMap() + self::$attributeMap;
     }
@@ -199,9 +196,9 @@ class ChildWithNullable extends ParentWithNullable
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return parent::setters() + self::$setters;
     }
@@ -209,9 +206,9 @@ class ChildWithNullable extends ParentWithNullable
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return parent::getters() + self::$getters;
     }
@@ -221,7 +218,7 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -231,8 +228,7 @@ class ChildWithNullable extends ParentWithNullable
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -250,7 +246,7 @@ class ChildWithNullable extends ParentWithNullable
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -262,9 +258,9 @@ class ChildWithNullable extends ParentWithNullable
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = parent::listInvalidProperties();
 
@@ -277,7 +273,7 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -288,7 +284,7 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return string|null
      */
-    public function getOtherProperty()
+    public function getOtherProperty(): ?string
     {
         return $this->container['other_property'];
     }
@@ -298,12 +294,12 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @param string|null $other_property other_property
      *
-     * @return self
+     * @return $this
      */
-    public function setOtherProperty($other_property)
+    public function setOtherProperty(?string $other_property): static
     {
         if (is_null($other_property)) {
-            throw new \InvalidArgumentException('non-nullable other_property cannot be null');
+            throw new InvalidArgumentException('non-nullable other_property cannot be null');
         }
         $this->container['other_property'] = $other_property;
 
@@ -316,7 +312,7 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -328,8 +324,8 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -342,7 +338,7 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -358,7 +354,7 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -370,8 +366,8 @@ class ChildWithNullable extends ParentWithNullable
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -381,7 +377,7 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -394,7 +390,7 @@ class ChildWithNullable extends ParentWithNullable
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/ParentWithNullable.php

@@ -28,8 +28,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * ParentWithNullable Class Doc Comment
@@ -38,9 +41,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializable
+class ParentWithNullable implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = 'type';
 
@@ -49,14 +52,14 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
       *
       * @var string
       */
-    protected static $openAPIModelName = 'ParentWithNullable';
+    protected static string $openAPIModelName = 'ParentWithNullable';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'type' => 'string',
         'nullable_property' => 'string'
     ];
@@ -64,11 +67,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'type' => null,
         'nullable_property' => null
     ];
@@ -76,7 +77,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'type' => false,
@@ -86,16 +87,16 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -103,9 +104,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -113,7 +114,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -123,7 +124,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -133,7 +134,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -166,9 +167,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'type' => 'type',
         'nullable_property' => 'nullableProperty'
     ];
@@ -176,9 +177,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'type' => 'setType',
         'nullable_property' => 'setNullableProperty'
     ];
@@ -186,9 +187,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'type' => 'getType',
         'nullable_property' => 'getNullableProperty'
     ];
@@ -197,9 +198,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -207,9 +208,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -217,9 +218,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -229,7 +230,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -251,15 +252,14 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -279,7 +279,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -291,9 +291,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -315,7 +315,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -326,7 +326,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return string|null
      */
-    public function getType()
+    public function getType(): ?string
     {
         return $this->container['type'];
     }
@@ -336,16 +336,16 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @param string|null $type type
      *
-     * @return self
+     * @return $this
      */
-    public function setType($type)
+    public function setType(?string $type): static
     {
         if (is_null($type)) {
-            throw new \InvalidArgumentException('non-nullable type cannot be null');
+            throw new InvalidArgumentException('non-nullable type cannot be null');
         }
         $allowedValues = $this->getTypeAllowableValues();
         if (!in_array($type, $allowedValues, true)) {
-            throw new \InvalidArgumentException(
+            throw new InvalidArgumentException(
                 sprintf(
                     "Invalid value '%s' for 'type', must be one of '%s'",
                     $type,
@@ -363,7 +363,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return string|null
      */
-    public function getNullableProperty()
+    public function getNullableProperty(): ?string
     {
         return $this->container['nullable_property'];
     }
@@ -373,9 +373,9 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @param string|null $nullable_property nullable_property
      *
-     * @return self
+     * @return $this
      */
-    public function setNullableProperty($nullable_property)
+    public function setNullableProperty(?string $nullable_property): static
     {
         if (is_null($nullable_property)) {
             array_push($this->openAPINullablesSetToNull, 'nullable_property');
@@ -398,7 +398,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -410,8 +410,8 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -424,7 +424,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -440,7 +440,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -452,8 +452,8 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -463,7 +463,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -476,7 +476,7 @@ class ParentWithNullable implements ModelInterface, ArrayAccess, \JsonSerializab
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }

samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/TestInlineFreeformAdditionalPropertiesRequest.php

@@ -28,8 +28,11 @@
 
 namespace OpenAPI\Client\Model;
 
-use \ArrayAccess;
-use \OpenAPI\Client\ObjectSerializer;
+use ArrayAccess;
+use JsonSerializable;
+use InvalidArgumentException;
+use ReturnTypeWillChange;
+use OpenAPI\Client\ObjectSerializer;
 
 /**
  * TestInlineFreeformAdditionalPropertiesRequest Class Doc Comment
@@ -38,9 +41,9 @@ use \OpenAPI\Client\ObjectSerializer;
  * @package  OpenAPI\Client
  * @author   OpenAPI Generator team
  * @link     https://openapi-generator.tech
- * @implements \ArrayAccess<string, mixed>
+ * @implements ArrayAccess<string, mixed>
  */
-class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, ArrayAccess, \JsonSerializable
+class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, ArrayAccess, JsonSerializable
 {
     public const DISCRIMINATOR = null;
 
@@ -49,32 +52,30 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
       *
       * @var string
       */
-    protected static $openAPIModelName = 'testInlineFreeformAdditionalProperties_request';
+    protected static string $openAPIModelName = 'testInlineFreeformAdditionalProperties_request';
 
     /**
       * Array of property to type mappings. Used for (de)serialization
       *
-      * @var string[]
+      * @var array<string, string>
       */
-    protected static $openAPITypes = [
+    protected static array $openAPITypes = [
         'some_property' => 'string'
     ];
 
     /**
       * Array of property to format mappings. Used for (de)serialization
       *
-      * @var string[]
-      * @phpstan-var array<string, string|null>
-      * @psalm-var array<string, string|null>
+      * @var array<string, string|null>
       */
-    protected static $openAPIFormats = [
+    protected static array $openAPIFormats = [
         'some_property' => null
     ];
 
     /**
       * Array of nullable properties. Used for (de)serialization
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected static array $openAPINullables = [
         'some_property' => false
@@ -83,16 +84,16 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
       * If a nullable field gets set to null, insert it here
       *
-      * @var boolean[]
+      * @var array<string, bool>
       */
     protected array $openAPINullablesSetToNull = [];
 
     /**
      * Array of property to type mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPITypes()
+    public static function openAPITypes(): array
     {
         return self::$openAPITypes;
     }
@@ -100,9 +101,9 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
      * Array of property to format mappings. Used for (de)serialization
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function openAPIFormats()
+    public static function openAPIFormats(): array
     {
         return self::$openAPIFormats;
     }
@@ -110,7 +111,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
      * Array of nullable properties
      *
-     * @return array
+     * @return array<string, bool>
      */
     protected static function openAPINullables(): array
     {
@@ -120,7 +121,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
      * Array of nullable field names deliberately set to null
      *
-     * @return boolean[]
+     * @return array<string, bool>
      */
     private function getOpenAPINullablesSetToNull(): array
     {
@@ -130,7 +131,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
      * Setter - Array of nullable field names deliberately set to null
      *
-     * @param boolean[] $openAPINullablesSetToNull
+     * @param array<string, bool> $openAPINullablesSetToNull
      */
     private function setOpenAPINullablesSetToNull(array $openAPINullablesSetToNull): void
     {
@@ -163,27 +164,27 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $attributeMap = [
+    protected static array $attributeMap = [
         'some_property' => 'someProperty'
     ];
 
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $setters = [
+    protected static array $setters = [
         'some_property' => 'setSomeProperty'
     ];
 
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @var string[]
+     * @var array<string, string>
      */
-    protected static $getters = [
+    protected static array $getters = [
         'some_property' => 'getSomeProperty'
     ];
 
@@ -191,9 +192,9 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      * Array of attributes where the key is the local name,
      * and the value is the original name
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function attributeMap()
+    public static function attributeMap(): array
     {
         return self::$attributeMap;
     }
@@ -201,9 +202,9 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
      * Array of attributes to setter functions (for deserialization of responses)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function setters()
+    public static function setters(): array
     {
         return self::$setters;
     }
@@ -211,9 +212,9 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
      * Array of attributes to getter functions (for serialization of requests)
      *
-     * @return array
+     * @return array<string, string>
      */
-    public static function getters()
+    public static function getters(): array
     {
         return self::$getters;
     }
@@ -223,7 +224,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return string
      */
-    public function getModelName()
+    public function getModelName(): string
     {
         return self::$openAPIModelName;
     }
@@ -232,15 +233,14 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
      * Associative array for storing property values
      *
-     * @var mixed[]
+     * @var array
      */
-    protected $container = [];
+    protected array $container = [];
 
     /**
      * Constructor
      *
-     * @param mixed[] $data Associated array of property values
-     *                      initializing the model
+     * @param array $data Associated array of property values initializing the model
      */
     public function __construct(array $data = null)
     {
@@ -256,7 +256,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     * @param array  $fields
     * @param mixed  $defaultValue
     */
-    private function setIfExists(string $variableName, array $fields, $defaultValue): void
+    private function setIfExists(string $variableName, array $fields, mixed $defaultValue): void
     {
         if (self::isNullable($variableName) && array_key_exists($variableName, $fields) && is_null($fields[$variableName])) {
             $this->openAPINullablesSetToNull[] = $variableName;
@@ -268,9 +268,9 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
     /**
      * Show all the invalid properties with reasons.
      *
-     * @return array invalid properties with reasons
+     * @return string[] invalid properties with reasons
      */
-    public function listInvalidProperties()
+    public function listInvalidProperties(): array
     {
         $invalidProperties = [];
 
@@ -283,7 +283,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return bool True if all properties are valid
      */
-    public function valid()
+    public function valid(): bool
     {
         return count($this->listInvalidProperties()) === 0;
     }
@@ -294,7 +294,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return string|null
      */
-    public function getSomeProperty()
+    public function getSomeProperty(): ?string
     {
         return $this->container['some_property'];
     }
@@ -304,12 +304,12 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @param string|null $some_property some_property
      *
-     * @return self
+     * @return $this
      */
-    public function setSomeProperty($some_property)
+    public function setSomeProperty(?string $some_property): static
     {
         if (is_null($some_property)) {
-            throw new \InvalidArgumentException('non-nullable some_property cannot be null');
+            throw new InvalidArgumentException('non-nullable some_property cannot be null');
         }
         $this->container['some_property'] = $some_property;
 
@@ -322,7 +322,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return boolean
      */
-    public function offsetExists($offset): bool
+    public function offsetExists(mixed $offset): bool
     {
         return isset($this->container[$offset]);
     }
@@ -334,8 +334,8 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return mixed|null
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    #[ReturnTypeWillChange]
+    public function offsetGet(mixed $offset): mixed
     {
         return $this->container[$offset] ?? null;
     }
@@ -348,7 +348,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return void
      */
-    public function offsetSet($offset, $value): void
+    public function offsetSet(mixed $offset, mixed $value): void
     {
         if (is_null($offset)) {
             $this->container[] = $value;
@@ -364,7 +364,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return void
      */
-    public function offsetUnset($offset): void
+    public function offsetUnset(mixed $offset): void
     {
         unset($this->container[$offset]);
     }
@@ -376,8 +376,8 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      * @return mixed Returns data which can be serialized by json_encode(), which is a value
      * of any type other than a resource.
      */
-    #[\ReturnTypeWillChange]
-    public function jsonSerialize()
+    #[ReturnTypeWillChange]
+    public function jsonSerialize(): mixed
     {
        return ObjectSerializer::sanitizeForSerialization($this);
     }
@@ -387,7 +387,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return json_encode(
             ObjectSerializer::sanitizeForSerialization($this),
@@ -400,7 +400,7 @@ class TestInlineFreeformAdditionalPropertiesRequest implements ModelInterface, A
      *
      * @return string
      */
-    public function toHeaderValue()
+    public function toHeaderValue(): string
     {
         return json_encode(ObjectSerializer::sanitizeForSerialization($this));
     }