[php] Fix file uploads by backporting #21458 (#21632)

* [php] Backport #21458 to php client

Fixes #21485

Credits to @jozefbriss

* [php] Fix deprecation warning when running integration tests

OpenAPI\Client\FakeHttpClient::setResponse(): Implicitly marking parameter $response as nullable is deprecated, the explicit nullable type must be used instead

---------

Co-authored-by: simonhammes <[email protected]>

Author: simonhammes

modules/openapi-generator/src/main/resources/php/FormDataProcessor.mustache

@@ -113,7 +113,11 @@ class FormDataProcessor
                     $currentName .= $currentSuffix;
                 }
 
-                $result[$currentName] = ObjectSerializer::toString($val);
+                if (is_resource($val)) {
+                    $result[$currentName] = $val;
+                } else {
+                    $result[$currentName] = ObjectSerializer::toString($val);
+                }
             }
 
             $currentName = $start;

samples/client/petstore/php/OpenAPIClient-php/lib/FormDataProcessor.php

@@ -121,7 +121,11 @@ 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;

samples/client/petstore/php/OpenAPIClient-php/tests/FakeHttpClient.php

@@ -27,7 +27,7 @@ public function getLastRequest()
     /**
      * @param null|ResponseInterface $response
      */
-    public function setResponse(ResponseInterface $response = null)
+    public function setResponse(?ResponseInterface $response = null)
     {
         $this->response = $response;
     }

samples/client/petstore/php/psr-18/lib/FormDataProcessor.php

@@ -121,7 +121,11 @@ 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;