diff --git a/samples/openapi3/client/petstore/php/SwaggerClient-php/docs/Api/FakeApi.md b/samples/openapi3/client/petstore/php/SwaggerClient-php/docs/Api/FakeApi.md
index 93a0a021bed..407ee95e994 100644
--- a/samples/openapi3/client/petstore/php/SwaggerClient-php/docs/Api/FakeApi.md
+++ b/samples/openapi3/client/petstore/php/SwaggerClient-php/docs/Api/FakeApi.md
@@ -294,8 +294,8 @@ $int64 = 56; // int | None
 $float = 3.4; // float | None
 $string = "string_example"; // string | None
 $binary = "binary_example"; // string | None
-$date = "date_example"; // \DateTime | None
-$date_time = "date_time_example"; // \DateTime | None
+$date = new \DateTime("2013-10-20T19:20:30+01:00"); // \DateTime | None
+$date_time = new \DateTime("2013-10-20T19:20:30+01:00"); // \DateTime | None
 $password = "password_example"; // string | None
 $callback = "callback_example"; // string | None
 
@@ -314,13 +314,13 @@ Name | Type | Description  | Notes
  **number** | **BigDecimal**| None |
  **double** | **double**| None |
  **pattern_without_delimiter** | **string**| None |
- **byte** | **string**| None |
+ **byte** | **string****string**| None |
  **integer** | **int**| None | [optional]
  **int32** | **int**| None | [optional]
  **int64** | **int**| None | [optional]
  **float** | **float**| None | [optional]
  **string** | **string**| None | [optional]
- **binary** | **string**| None | [optional]
+ **binary** | **string****string**| None | [optional]
  **date** | **\DateTime**| None | [optional]
  **date_time** | **\DateTime**| None | [optional]
  **password** | **string**| None | [optional]
diff --git a/samples/openapi3/client/petstore/php/SwaggerClient-php/docs/Api/PetApi.md b/samples/openapi3/client/petstore/php/SwaggerClient-php/docs/Api/PetApi.md
index dc6a9fb94e1..5beb474fe54 100644
--- a/samples/openapi3/client/petstore/php/SwaggerClient-php/docs/Api/PetApi.md
+++ b/samples/openapi3/client/petstore/php/SwaggerClient-php/docs/Api/PetApi.md
@@ -419,7 +419,7 @@ Name | Type | Description  | Notes
 ------------- | ------------- | ------------- | -------------
  **pet_id** | **int**| ID of pet to update |
  **additional_metadata** | **string**| Additional data to pass to server | [optional]
- **file** | **string**| file to upload | [optional]
+ **file** | **string****string**| file to upload | [optional]
 
 ### Return type
 
diff --git a/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Api/FakeApi.php b/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Api/FakeApi.php
index b35eda5bd31..306cf69eefb 100644
--- a/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Api/FakeApi.php
+++ b/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Api/FakeApi.php
@@ -1641,11 +1641,13 @@ class FakeApi
         }
         // form params
         if ($byte !== null) {
-            $formParams['byte'] = ObjectSerializer::toFormValue($byte);
+            $multipart = true;
+            $formParams['byte'] = \GuzzleHttp\Psr7\try_fopen(ObjectSerializer::toFormValue($byte), 'rb');
         }
         // form params
         if ($binary !== null) {
-            $formParams['binary'] = ObjectSerializer::toFormValue($binary);
+            $multipart = true;
+            $formParams['binary'] = \GuzzleHttp\Psr7\try_fopen(ObjectSerializer::toFormValue($binary), 'rb');
         }
         // form params
         if ($date !== null) {
diff --git a/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Api/PetApi.php b/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Api/PetApi.php
index a0fb0b9a48e..302392042a1 100644
--- a/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Api/PetApi.php
+++ b/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Api/PetApi.php
@@ -2031,7 +2031,8 @@ class PetApi
         }
         // form params
         if ($file !== null) {
-            $formParams['file'] = ObjectSerializer::toFormValue($file);
+            $multipart = true;
+            $formParams['file'] = \GuzzleHttp\Psr7\try_fopen(ObjectSerializer::toFormValue($file), 'rb');
         }
         // body params
         $_tempBody = null;
diff --git a/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Model/Body3.php b/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Model/Body3.php
index 1d5e6732eb1..cf6c0709d8d 100644
--- a/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Model/Body3.php
+++ b/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Model/Body3.php
@@ -295,11 +295,11 @@ class Body3 implements ModelInterface, ArrayAccess
         if ($this->container['byte'] === null) {
             $invalidProperties[] = "'byte' can't be null";
         }
-        if (!is_null($this->container['password']) && (strlen($this->container['password']) > 64)) {
+        if (!is_null($this->container['password']) && (mb_strlen($this->container['password']) > 64)) {
             $invalidProperties[] = "invalid value for 'password', the character length must be smaller than or equal to 64.";
         }
 
-        if (!is_null($this->container['password']) && (strlen($this->container['password']) < 10)) {
+        if (!is_null($this->container['password']) && (mb_strlen($this->container['password']) < 10)) {
             $invalidProperties[] = "invalid value for 'password', the character length must be bigger than or equal to 10.";
         }
 
@@ -339,10 +339,10 @@ class Body3 implements ModelInterface, ArrayAccess
         if ($this->container['byte'] === null) {
             return false;
         }
-        if (strlen($this->container['password']) > 64) {
+        if (mb_strlen($this->container['password']) > 64) {
             return false;
         }
-        if (strlen($this->container['password']) < 10) {
+        if (mb_strlen($this->container['password']) < 10) {
             return false;
         }
         return true;
@@ -672,10 +672,10 @@ class Body3 implements ModelInterface, ArrayAccess
      */
     public function setPassword($password)
     {
-        if (!is_null($password) && (strlen($password) > 64)) {
+        if (!is_null($password) && (mb_strlen($password) > 64)) {
             throw new \InvalidArgumentException('invalid length for $password when calling Body3., must be smaller than or equal to 64.');
         }
-        if (!is_null($password) && (strlen($password) < 10)) {
+        if (!is_null($password) && (mb_strlen($password) < 10)) {
             throw new \InvalidArgumentException('invalid length for $password when calling Body3., must be bigger than or equal to 10.');
         }
 
diff --git a/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Model/FormatTest.php b/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Model/FormatTest.php
index b80143dbc3a..9210ba363d0 100644
--- a/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Model/FormatTest.php
+++ b/samples/openapi3/client/petstore/php/SwaggerClient-php/lib/Model/FormatTest.php
@@ -289,11 +289,11 @@ class FormatTest implements ModelInterface, ArrayAccess
         if ($this->container['password'] === null) {
             $invalidProperties[] = "'password' can't be null";
         }
-        if ((strlen($this->container['password']) > 64)) {
+        if ((mb_strlen($this->container['password']) > 64)) {
             $invalidProperties[] = "invalid value for 'password', the character length must be smaller than or equal to 64.";
         }
 
-        if ((strlen($this->container['password']) < 10)) {
+        if ((mb_strlen($this->container['password']) < 10)) {
             $invalidProperties[] = "invalid value for 'password', the character length must be bigger than or equal to 10.";
         }
 
@@ -333,10 +333,10 @@ class FormatTest implements ModelInterface, ArrayAccess
         if ($this->container['password'] === null) {
             return false;
         }
-        if (strlen($this->container['password']) > 64) {
+        if (mb_strlen($this->container['password']) > 64) {
             return false;
         }
-        if (strlen($this->container['password']) < 10) {
+        if (mb_strlen($this->container['password']) < 10) {
             return false;
         }
         return true;
@@ -666,10 +666,10 @@ class FormatTest implements ModelInterface, ArrayAccess
      */
     public function setPassword($password)
     {
-        if ((strlen($password) > 64)) {
+        if ((mb_strlen($password) > 64)) {
             throw new \InvalidArgumentException('invalid length for $password when calling FormatTest., must be smaller than or equal to 64.');
         }
-        if ((strlen($password) < 10)) {
+        if ((mb_strlen($password) < 10)) {
             throw new \InvalidArgumentException('invalid length for $password when calling FormatTest., must be bigger than or equal to 10.');
         }