public static function fetchData($url, $fields = array())
 {
     $id = Video_Fetcher::extractIDFromURL($url);
     $channel = Video_Fetcher::extractChanneldFromURL($url);
     switch ($channel) {
         case 'youtube':
             return Video_Fetcher::fetchYoutubeData($id, $fields);
         case 'vimeo':
             return Video_Fetcher::fetchVimeoData($id, $fields);
         default:
             return null;
     }
 }