diff --git a/modules/openapi-generator/src/main/resources/php/api.mustache b/modules/openapi-generator/src/main/resources/php/api.mustache
index b1b9dd3bf10..fedb7d53241 100644
--- a/modules/openapi-generator/src/main/resources/php/api.mustache
+++ b/modules/openapi-generator/src/main/resources/php/api.mustache
@@ -688,6 +688,9 @@ use {{invokerPackage}}\ObjectSerializer;
         }
         {{/formParams}}
 
+        {{#isMultipart}}
+        $multipart = true;
+        {{/isMultipart}}
         $headers = $this->headerSelector->selectHeaders(
             [{{#produces}}'{{{mediaType}}}', {{/produces}}],
             $contentType,
diff --git a/samples/client/petstore/php/OpenAPIClient-php/lib/Api/PetApi.php b/samples/client/petstore/php/OpenAPIClient-php/lib/Api/PetApi.php
index 872b2f8607b..a8ed1dae0a0 100644
--- a/samples/client/petstore/php/OpenAPIClient-php/lib/Api/PetApi.php
+++ b/samples/client/petstore/php/OpenAPIClient-php/lib/Api/PetApi.php
@@ -2571,6 +2571,7 @@ class PetApi
             }
         }
 
+        $multipart = true;
         $headers = $this->headerSelector->selectHeaders(
             ['application/json', ],
             $contentType,
@@ -2917,6 +2918,7 @@ class PetApi
             }
         }
 
+        $multipart = true;
         $headers = $this->headerSelector->selectHeaders(
             ['application/json', ],
             $contentType,