public function login($service, $gateway = false)
    {
        $query = array(
            'service' => $this->my_service . '?' . http_build_query(array(
                    'service' => $service,
                )),
        );
        if ($gateway) {
            $query['gateway'] = $gateway;
        }
        self::http_redirect($this->server['login_url'] . '?' . http_build_query($query));
        // never reach
        return true;
    }