protected static function fe()
    {
        if( ! empty(ZN::upgrade()) )
        {
            $status = self::$lang['upgradeSuccess'];
        }
        else
        {
            $status = self::$lang['alreadyVersion'];

            if( $upgradeError = ZN::upgradeError() )
            {
                $status = $upgradeError;
            }         
        }

        return $status;
    }