private static function GetCredentials()
 {
     if (empty(self::$appid) || empty(self::$key)) {
         $data = json_decode(file_get_contents(dirname(__FILE__) . '/data/config.json'), true);
         self::$appid = $data['op']['appid'];
         self::$key = $data['op']['key'];
     }
     return true;
 }