获取accesstoken的问题

       if(isset($_SESSION['access_token'])&&$_SESSION['expire_time']>time()){

            return $_SESSION['access_token'];

        }else{

            $access_token = $this -> access_token();

            $url='https://api.weixin.qq.com/cgi-bin/menu/create?access_token=' . $access_token['access_token'];

            $this->curl($url,$data);

            $_SESSION['access_token']=$access_token['access_token'];

            $_SESSION['expire_time']=time()+7200;

        }

        echo $_SESSION['access_token'];