public function back($service, $ticket = '')
    {
        $parts = parse_url($service);
        if (isset($parts['query'])) {
            parse_str($parts['query'], $query);
        } else {
            $query = array();
        }
        if (!empty($ticket)) {
            $query['ticket'] = $ticket;
        }
        $parts['query'] = http_build_query($query);
        self::http_redirect(self::build_url($parts));
        // never reach
        return true;
    }