diff --git a/modules/swagger-codegen/src/main/resources/php/api.mustache b/modules/swagger-codegen/src/main/resources/php/api.mustache
index 7ba928ce1848..2ef85004c4b1 100644
--- a/modules/swagger-codegen/src/main/resources/php/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/php/api.mustache
@@ -23,6 +23,7 @@ use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
 use {{invokerPackage}}\ApiException;
 use {{invokerPackage}}\Configuration;
 use {{invokerPackage}}\HeaderSelector;
@@ -122,9 +123,9 @@ use {{invokerPackage}}\ObjectSerializer;
         $request = $this->{{operationId}}Request({{#allParams}}${{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}});
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -236,7 +237,7 @@ use {{invokerPackage}}\ObjectSerializer;
         $request = $this->{{operationId}}Request({{#allParams}}${{paramName}}{{#hasMore}}, {{/hasMore}}{{/allParams}});
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     {{#returnType}}
@@ -487,5 +488,23 @@ use {{invokerPackage}}\ObjectSerializer;
     }
 
     {{/operation}}
+    /**
+     * Create http client option
+     *
+     * @throws \RuntimeException on file opening failure
+     * @return array of http client options
+     */
+    protected function createHttpClientOption()
+    {
+        $options = [];
+        if ($this->config->getDebug()) {
+            $options[RequestOptions::DEBUG] = fopen($this->config->getDebugFile(), 'a');
+            if (!$options[RequestOptions::DEBUG]) {
+                throw new \RuntimeException('Failed to open the debug file: ' . $this->config->getDebugFile());
+            }
+        }
+
+        return $options;
+    }
 }
 {{/operations}}
diff --git a/samples/client/petstore-security-test/php/SwaggerClient-php/lib/Api/FakeApi.php b/samples/client/petstore-security-test/php/SwaggerClient-php/lib/Api/FakeApi.php
index 16ad474af261..bf65cbac5d00 100644
--- a/samples/client/petstore-security-test/php/SwaggerClient-php/lib/Api/FakeApi.php
+++ b/samples/client/petstore-security-test/php/SwaggerClient-php/lib/Api/FakeApi.php
@@ -32,6 +32,7 @@ use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
 use Swagger\Client\ApiException;
 use Swagger\Client\Configuration;
 use Swagger\Client\HeaderSelector;
@@ -113,9 +114,9 @@ class FakeApi
         $request = $this->testCodeInjectEndRnNRRequest($test_code_inject____end____rn_n_r);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -184,7 +185,7 @@ class FakeApi
         $request = $this->testCodeInjectEndRnNRRequest($test_code_inject____end____rn_n_r);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -294,4 +295,22 @@ class FakeApi
         );
     }
 
+    /**
+     * Create http client option
+     *
+     * @throws \RuntimeException on file opening failure
+     * @return array of http client options
+     */
+    protected function createHttpClientOption()
+    {
+        $options = [];
+        if ($this->config->getDebug()) {
+            $options[RequestOptions::DEBUG] = fopen($this->config->getDebugFile(), 'a');
+            if (!$options[RequestOptions::DEBUG]) {
+                throw new \RuntimeException('Failed to open the debug file: ' . $this->config->getDebugFile());
+            }
+        }
+
+        return $options;
+    }
 }
diff --git a/samples/client/petstore/php/SwaggerClient-php/lib/Api/AnotherFakeApi.php b/samples/client/petstore/php/SwaggerClient-php/lib/Api/AnotherFakeApi.php
index a5980f76cc21..a56487fc0629 100644
--- a/samples/client/petstore/php/SwaggerClient-php/lib/Api/AnotherFakeApi.php
+++ b/samples/client/petstore/php/SwaggerClient-php/lib/Api/AnotherFakeApi.php
@@ -32,6 +32,7 @@ use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
 use Swagger\Client\ApiException;
 use Swagger\Client\Configuration;
 use Swagger\Client\HeaderSelector;
@@ -114,9 +115,9 @@ class AnotherFakeApi
         $request = $this->testSpecialTagsRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -207,7 +208,7 @@ class AnotherFakeApi
         $request = $this->testSpecialTagsRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -336,4 +337,22 @@ class AnotherFakeApi
         );
     }
 
+    /**
+     * Create http client option
+     *
+     * @throws \RuntimeException on file opening failure
+     * @return array of http client options
+     */
+    protected function createHttpClientOption()
+    {
+        $options = [];
+        if ($this->config->getDebug()) {
+            $options[RequestOptions::DEBUG] = fopen($this->config->getDebugFile(), 'a');
+            if (!$options[RequestOptions::DEBUG]) {
+                throw new \RuntimeException('Failed to open the debug file: ' . $this->config->getDebugFile());
+            }
+        }
+
+        return $options;
+    }
 }
diff --git a/samples/client/petstore/php/SwaggerClient-php/lib/Api/FakeApi.php b/samples/client/petstore/php/SwaggerClient-php/lib/Api/FakeApi.php
index 61d4e4a3095a..4df01fca5032 100644
--- a/samples/client/petstore/php/SwaggerClient-php/lib/Api/FakeApi.php
+++ b/samples/client/petstore/php/SwaggerClient-php/lib/Api/FakeApi.php
@@ -32,6 +32,7 @@ use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
 use Swagger\Client\ApiException;
 use Swagger\Client\Configuration;
 use Swagger\Client\HeaderSelector;
@@ -110,9 +111,9 @@ class FakeApi
         $request = $this->fakeOuterBooleanSerializeRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -203,7 +204,7 @@ class FakeApi
         $request = $this->fakeOuterBooleanSerializeRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -356,9 +357,9 @@ class FakeApi
         $request = $this->fakeOuterCompositeSerializeRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -449,7 +450,7 @@ class FakeApi
         $request = $this->fakeOuterCompositeSerializeRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -602,9 +603,9 @@ class FakeApi
         $request = $this->fakeOuterNumberSerializeRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -695,7 +696,7 @@ class FakeApi
         $request = $this->fakeOuterNumberSerializeRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -848,9 +849,9 @@ class FakeApi
         $request = $this->fakeOuterStringSerializeRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -941,7 +942,7 @@ class FakeApi
         $request = $this->fakeOuterStringSerializeRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -1098,9 +1099,9 @@ class FakeApi
         $request = $this->testClientModelRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1191,7 +1192,7 @@ class FakeApi
         $request = $this->testClientModelRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -1379,9 +1380,9 @@ class FakeApi
         $request = $this->testEndpointParametersRequest($number, $double, $pattern_without_delimiter, $byte, $integer, $int32, $int64, $float, $string, $binary, $date, $date_time, $password, $callback);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1476,7 +1477,7 @@ class FakeApi
         $request = $this->testEndpointParametersRequest($number, $double, $pattern_without_delimiter, $byte, $integer, $int32, $int64, $float, $string, $binary, $date, $date_time, $password, $callback);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -1773,9 +1774,9 @@ class FakeApi
         $request = $this->testEnumParametersRequest($enum_form_string_array, $enum_form_string, $enum_header_string_array, $enum_header_string, $enum_query_string_array, $enum_query_string, $enum_query_integer, $enum_query_double);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1858,7 +1859,7 @@ class FakeApi
         $request = $this->testEnumParametersRequest($enum_form_string_array, $enum_form_string, $enum_header_string_array, $enum_header_string, $enum_query_string_array, $enum_query_string, $enum_query_integer, $enum_query_double);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -2042,9 +2043,9 @@ class FakeApi
         $request = $this->testInlineAdditionalPropertiesRequest($param);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -2113,7 +2114,7 @@ class FakeApi
         $request = $this->testInlineAdditionalPropertiesRequest($param);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -2263,9 +2264,9 @@ class FakeApi
         $request = $this->testJsonFormDataRequest($param, $param2);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -2336,7 +2337,7 @@ class FakeApi
         $request = $this->testJsonFormDataRequest($param, $param2);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -2463,4 +2464,22 @@ class FakeApi
         );
     }
 
+    /**
+     * Create http client option
+     *
+     * @throws \RuntimeException on file opening failure
+     * @return array of http client options
+     */
+    protected function createHttpClientOption()
+    {
+        $options = [];
+        if ($this->config->getDebug()) {
+            $options[RequestOptions::DEBUG] = fopen($this->config->getDebugFile(), 'a');
+            if (!$options[RequestOptions::DEBUG]) {
+                throw new \RuntimeException('Failed to open the debug file: ' . $this->config->getDebugFile());
+            }
+        }
+
+        return $options;
+    }
 }
diff --git a/samples/client/petstore/php/SwaggerClient-php/lib/Api/FakeClassnameTags123Api.php b/samples/client/petstore/php/SwaggerClient-php/lib/Api/FakeClassnameTags123Api.php
index 3e306d423a3e..621058189636 100644
--- a/samples/client/petstore/php/SwaggerClient-php/lib/Api/FakeClassnameTags123Api.php
+++ b/samples/client/petstore/php/SwaggerClient-php/lib/Api/FakeClassnameTags123Api.php
@@ -32,6 +32,7 @@ use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
 use Swagger\Client\ApiException;
 use Swagger\Client\Configuration;
 use Swagger\Client\HeaderSelector;
@@ -114,9 +115,9 @@ class FakeClassnameTags123Api
         $request = $this->testClassnameRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -207,7 +208,7 @@ class FakeClassnameTags123Api
         $request = $this->testClassnameRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -341,4 +342,22 @@ class FakeClassnameTags123Api
         );
     }
 
+    /**
+     * Create http client option
+     *
+     * @throws \RuntimeException on file opening failure
+     * @return array of http client options
+     */
+    protected function createHttpClientOption()
+    {
+        $options = [];
+        if ($this->config->getDebug()) {
+            $options[RequestOptions::DEBUG] = fopen($this->config->getDebugFile(), 'a');
+            if (!$options[RequestOptions::DEBUG]) {
+                throw new \RuntimeException('Failed to open the debug file: ' . $this->config->getDebugFile());
+            }
+        }
+
+        return $options;
+    }
 }
diff --git a/samples/client/petstore/php/SwaggerClient-php/lib/Api/PetApi.php b/samples/client/petstore/php/SwaggerClient-php/lib/Api/PetApi.php
index 313e0f2882d3..80f41fdf971d 100644
--- a/samples/client/petstore/php/SwaggerClient-php/lib/Api/PetApi.php
+++ b/samples/client/petstore/php/SwaggerClient-php/lib/Api/PetApi.php
@@ -32,6 +32,7 @@ use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
 use Swagger\Client\ApiException;
 use Swagger\Client\Configuration;
 use Swagger\Client\HeaderSelector;
@@ -113,9 +114,9 @@ class PetApi
         $request = $this->addPetRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -184,7 +185,7 @@ class PetApi
         $request = $this->addPetRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -338,9 +339,9 @@ class PetApi
         $request = $this->deletePetRequest($pet_id, $api_key);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -411,7 +412,7 @@ class PetApi
         $request = $this->deletePetRequest($pet_id, $api_key);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -574,9 +575,9 @@ class PetApi
         $request = $this->findPetsByStatusRequest($status);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -667,7 +668,7 @@ class PetApi
         $request = $this->findPetsByStatusRequest($status);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -838,9 +839,9 @@ class PetApi
         $request = $this->findPetsByTagsRequest($tags);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -931,7 +932,7 @@ class PetApi
         $request = $this->findPetsByTagsRequest($tags);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -1102,9 +1103,9 @@ class PetApi
         $request = $this->getPetByIdRequest($pet_id);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1195,7 +1196,7 @@ class PetApi
         $request = $this->getPetByIdRequest($pet_id);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -1367,9 +1368,9 @@ class PetApi
         $request = $this->updatePetRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1438,7 +1439,7 @@ class PetApi
         $request = $this->updatePetRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -1594,9 +1595,9 @@ class PetApi
         $request = $this->updatePetWithFormRequest($pet_id, $name, $status);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1669,7 +1670,7 @@ class PetApi
         $request = $this->updatePetWithFormRequest($pet_id, $name, $status);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -1841,9 +1842,9 @@ class PetApi
         $request = $this->uploadFileRequest($pet_id, $additional_metadata, $file);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1938,7 +1939,7 @@ class PetApi
         $request = $this->uploadFileRequest($pet_id, $additional_metadata, $file);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -2087,4 +2088,22 @@ class PetApi
         );
     }
 
+    /**
+     * Create http client option
+     *
+     * @throws \RuntimeException on file opening failure
+     * @return array of http client options
+     */
+    protected function createHttpClientOption()
+    {
+        $options = [];
+        if ($this->config->getDebug()) {
+            $options[RequestOptions::DEBUG] = fopen($this->config->getDebugFile(), 'a');
+            if (!$options[RequestOptions::DEBUG]) {
+                throw new \RuntimeException('Failed to open the debug file: ' . $this->config->getDebugFile());
+            }
+        }
+
+        return $options;
+    }
 }
diff --git a/samples/client/petstore/php/SwaggerClient-php/lib/Api/StoreApi.php b/samples/client/petstore/php/SwaggerClient-php/lib/Api/StoreApi.php
index 9424f62693e5..175f939a7e6b 100644
--- a/samples/client/petstore/php/SwaggerClient-php/lib/Api/StoreApi.php
+++ b/samples/client/petstore/php/SwaggerClient-php/lib/Api/StoreApi.php
@@ -32,6 +32,7 @@ use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
 use Swagger\Client\ApiException;
 use Swagger\Client\Configuration;
 use Swagger\Client\HeaderSelector;
@@ -113,9 +114,9 @@ class StoreApi
         $request = $this->deleteOrderRequest($order_id);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -184,7 +185,7 @@ class StoreApi
         $request = $this->deleteOrderRequest($order_id);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -336,9 +337,9 @@ class StoreApi
         $request = $this->getInventoryRequest();
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -427,7 +428,7 @@ class StoreApi
         $request = $this->getInventoryRequest();
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -585,9 +586,9 @@ class StoreApi
         $request = $this->getOrderByIdRequest($order_id);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -678,7 +679,7 @@ class StoreApi
         $request = $this->getOrderByIdRequest($order_id);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -853,9 +854,9 @@ class StoreApi
         $request = $this->placeOrderRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -946,7 +947,7 @@ class StoreApi
         $request = $this->placeOrderRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -1075,4 +1076,22 @@ class StoreApi
         );
     }
 
+    /**
+     * Create http client option
+     *
+     * @throws \RuntimeException on file opening failure
+     * @return array of http client options
+     */
+    protected function createHttpClientOption()
+    {
+        $options = [];
+        if ($this->config->getDebug()) {
+            $options[RequestOptions::DEBUG] = fopen($this->config->getDebugFile(), 'a');
+            if (!$options[RequestOptions::DEBUG]) {
+                throw new \RuntimeException('Failed to open the debug file: ' . $this->config->getDebugFile());
+            }
+        }
+
+        return $options;
+    }
 }
diff --git a/samples/client/petstore/php/SwaggerClient-php/lib/Api/UserApi.php b/samples/client/petstore/php/SwaggerClient-php/lib/Api/UserApi.php
index ce31171cef12..523da183ae65 100644
--- a/samples/client/petstore/php/SwaggerClient-php/lib/Api/UserApi.php
+++ b/samples/client/petstore/php/SwaggerClient-php/lib/Api/UserApi.php
@@ -32,6 +32,7 @@ use GuzzleHttp\ClientInterface;
 use GuzzleHttp\Exception\RequestException;
 use GuzzleHttp\Psr7\MultipartStream;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
 use Swagger\Client\ApiException;
 use Swagger\Client\Configuration;
 use Swagger\Client\HeaderSelector;
@@ -113,9 +114,9 @@ class UserApi
         $request = $this->createUserRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -184,7 +185,7 @@ class UserApi
         $request = $this->createUserRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -332,9 +333,9 @@ class UserApi
         $request = $this->createUsersWithArrayInputRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -403,7 +404,7 @@ class UserApi
         $request = $this->createUsersWithArrayInputRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -551,9 +552,9 @@ class UserApi
         $request = $this->createUsersWithListInputRequest($body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -622,7 +623,7 @@ class UserApi
         $request = $this->createUsersWithListInputRequest($body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -770,9 +771,9 @@ class UserApi
         $request = $this->deleteUserRequest($username);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -841,7 +842,7 @@ class UserApi
         $request = $this->deleteUserRequest($username);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -995,9 +996,9 @@ class UserApi
         $request = $this->getUserByNameRequest($username);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1088,7 +1089,7 @@ class UserApi
         $request = $this->getUserByNameRequest($username);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -1258,9 +1259,9 @@ class UserApi
         $request = $this->loginUserRequest($username, $password);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1353,7 +1354,7 @@ class UserApi
         $request = $this->loginUserRequest($username, $password);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     $responseBody = $response->getBody();
@@ -1525,9 +1526,9 @@ class UserApi
         $request = $this->logoutUserRequest();
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1594,7 +1595,7 @@ class UserApi
         $request = $this->logoutUserRequest();
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -1734,9 +1735,9 @@ class UserApi
         $request = $this->updateUserRequest($username, $body);
 
         try {
-
+            $options = $this->createHttpClientOption();
             try {
-                $response = $this->client->send($request);
+                $response = $this->client->send($request, $options);
             } catch (RequestException $e) {
                 throw new ApiException(
                     "[{$e->getCode()}] {$e->getMessage()}",
@@ -1807,7 +1808,7 @@ class UserApi
         $request = $this->updateUserRequest($username, $body);
 
         return $this->client
-            ->sendAsync($request)
+            ->sendAsync($request, $this->createHttpClientOption())
             ->then(
                 function ($response) use ($returnType) {
                     return [null, $response->getStatusCode(), $response->getHeaders()];
@@ -1937,4 +1938,22 @@ class UserApi
         );
     }
 
+    /**
+     * Create http client option
+     *
+     * @throws \RuntimeException on file opening failure
+     * @return array of http client options
+     */
+    protected function createHttpClientOption()
+    {
+        $options = [];
+        if ($this->config->getDebug()) {
+            $options[RequestOptions::DEBUG] = fopen($this->config->getDebugFile(), 'a');
+            if (!$options[RequestOptions::DEBUG]) {
+                throw new \RuntimeException('Failed to open the debug file: ' . $this->config->getDebugFile());
+            }
+        }
+
+        return $options;
+    }
 }
diff --git a/samples/client/petstore/php/SwaggerClient-php/tests/DebugTest.php b/samples/client/petstore/php/SwaggerClient-php/tests/DebugTest.php
new file mode 100644
index 000000000000..6eb9dacaffeb
--- /dev/null
+++ b/samples/client/petstore/php/SwaggerClient-php/tests/DebugTest.php
@@ -0,0 +1,26 @@
+<?php
+namespace Swagger\Client;
+
+class DebugTest extends \PHPUnit_Framework_TestCase
+{
+    public function testEnableDebugOutput()
+    {
+        $this->expectOutputRegex('#GET /v2/pet/1 HTTP/1.1#');
+
+        $config = new Configuration();
+        $config->setDebug(true);
+        $api = new Api\PetApi(null, $config);
+        $api->getPetById(1);
+    }
+
+    public function testEnableDebugOutputAsync()
+    {
+        $this->expectOutputRegex('#GET /v2/pet/1 HTTP/1.1#');
+
+        $config = new Configuration();
+        $config->setDebug(true);
+        $api = new Api\PetApi(null, $config);
+        $promise = $api->getPetByIdAsync(1);
+        $promise->wait();
+    }
+}