diff --git a/modules/openapi-generator/src/main/resources/php-nextgen/FormDataProcessor.mustache b/modules/openapi-generator/src/main/resources/php-nextgen/FormDataProcessor.mustache
index ad9808c4ab12..4f73458ecf81 100644
--- a/modules/openapi-generator/src/main/resources/php-nextgen/FormDataProcessor.mustache
+++ b/modules/openapi-generator/src/main/resources/php-nextgen/FormDataProcessor.mustache
@@ -104,7 +104,11 @@ class FormDataProcessor
                     $currentName .= $currentSuffix;
                 }
 
-                $result[$currentName] = ObjectSerializer::toString($val);
+                if (is_resource($val)) {
+                    $result[$currentName] = $val;
+                } else {
+                    $result[$currentName] = ObjectSerializer::toString($val);
+                }
             }
 
             $currentName = $start;
diff --git a/samples/client/echo_api/php-nextgen-streaming/src/FormDataProcessor.php b/samples/client/echo_api/php-nextgen-streaming/src/FormDataProcessor.php
index 4699219af6ba..402f90c0c586 100644
--- a/samples/client/echo_api/php-nextgen-streaming/src/FormDataProcessor.php
+++ b/samples/client/echo_api/php-nextgen-streaming/src/FormDataProcessor.php
@@ -114,7 +114,11 @@ public static function flatten(array $source, string $start = ''): array
                     $currentName .= $currentSuffix;
                 }
 
-                $result[$currentName] = ObjectSerializer::toString($val);
+                if (is_resource($val)) {
+                    $result[$currentName] = $val;
+                } else {
+                    $result[$currentName] = ObjectSerializer::toString($val);
+                }
             }
 
             $currentName = $start;
diff --git a/samples/client/echo_api/php-nextgen/src/FormDataProcessor.php b/samples/client/echo_api/php-nextgen/src/FormDataProcessor.php
index 4699219af6ba..402f90c0c586 100644
--- a/samples/client/echo_api/php-nextgen/src/FormDataProcessor.php
+++ b/samples/client/echo_api/php-nextgen/src/FormDataProcessor.php
@@ -114,7 +114,11 @@ public static function flatten(array $source, string $start = ''): array
                     $currentName .= $currentSuffix;
                 }
 
-                $result[$currentName] = ObjectSerializer::toString($val);
+                if (is_resource($val)) {
+                    $result[$currentName] = $val;
+                } else {
+                    $result[$currentName] = ObjectSerializer::toString($val);
+                }
             }
 
             $currentName = $start;
diff --git a/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/FormDataProcessor.php b/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/FormDataProcessor.php
index ea0897ce17fa..c6a2a185bf3a 100644
--- a/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/FormDataProcessor.php
+++ b/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/FormDataProcessor.php
@@ -113,7 +113,11 @@ public static function flatten(array $source, string $start = ''): array
                     $currentName .= $currentSuffix;
                 }
 
-                $result[$currentName] = ObjectSerializer::toString($val);
+                if (is_resource($val)) {
+                    $result[$currentName] = $val;
+                } else {
+                    $result[$currentName] = ObjectSerializer::toString($val);
+                }
             }
 
             $currentName = $start;