static function handleDone()
    {
        $return = null;

        if (!self::hasHandling())
            ## there is no error
            return $return;

        $stack = array_pop(self::$_STACK);
        if ($stack['has_handled_error'])
            $return = $stack['has_handled_error'];

        # restore error handler
        (($stack['error_type']) === self::ERR_TYP_ERROR)
            ? restore_error_handler()
            : restore_exception_handler()
        ;

        return $return;
    }