Symfony\Component\HttpFoundation\Request::getMimeTypes PHP Method

    public static function getMimeTypes($format)
    {
        if (null === static::$formats) {
            static::initializeFormats();
        }

        return isset(static::$formats[$format]) ? static::$formats[$format] : array();
    }

 private static function extendRequestFormats(Request $request, array $formats)
 {
     foreach ($formats as $format => $mimeTypes) {
         if (method_exists(get_class($request), 'getMimeTypes')) {
             $mimeTypes = array_merge($mimeTypes, Request::getMimeTypes($format));
         } elseif (null !== $request->getMimeType($format)) {
             $class = new \ReflectionClass(get_class($request));
             $properties = $class->getStaticProperties();
             if (isset($properties['formats'][$format])) {
                 $mimeTypes = array_merge($mimeTypes, $properties['formats'][$format]);
             }
         }
         $request->setFormat($format, array_unique($mimeTypes));
     }
 }