[PHP] Bugfix: DateTime object on query (#13583)

* [PHP] BUGFIX: fix code breaking when query params contain a DateTime object

* [PHP] Autogenerated files

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

@@ -189,6 +189,11 @@ class ObjectSerializer
             }
         }
 
+        # Handle DateTime objects in query
+        if($openApiType === "\\DateTime" && $value instanceof \DateTime) {
+            return ["{$paramName}" => $value->format(self::$dateTimeFormat)];
+        }
+
         $query = [];
         $value = (in_array($openApiType, ['object', 'array'], true)) ? (array)$value : $value;