/**
     * 统一API接口调用
     *
     * @param array $req_params 请求的参数数组
     * @param string $url_path 调用的接口PHP路径，不保含主机地址
     * @return array
     */
    static public function api($req_params, $url_path)
    {
        $req = array('sid' => self::$api_cfg['sid'], 'appkey' => self::$api_cfg['appkey'], 'timestamp' => time());
        $appSecret = self::$api_cfg['appsecret'];
        $pre_dir = self::$api_cfg['predir'];

        $req = array_merge($req, $req_params);
        self::makeSign($req, $appSecret);
        Log::LOG('wdt_api', "req param:" . print_r($req, true));
        $service_url = "http://" . self::$api_cfg['host'] . $pre_dir . $url_path . '?' . http_build_query($req);
        $response = file_get_contents($service_url);
        Log::LOG('wdt_api', "req url:" . $service_url);
        Log::LOG('wdt_api', $response);
        if ($response === false) return false;
        $json = json_decode($response, true);
        Log::LOG('wdt_api', "response:" . print_r($json, true));
        return $json;
    }