public function signCheck($request)
    {
        $sign = $request['sign'];

        if($sign === api_helper::getSign($request))
        {
            return true;
        }
        return false;
    }

    // api_helper
    public static function getSign($request)
    {
        $sign = $request['sign'];
        unset($request['sign']);

        return md5(md5(implode("",$request)));
    }