上面这段PHP后台登陆代码实现免登陆

下面这段PHP后台登陆代码实现免登陆
如果后台管理员帐号为admin,密码为123456请问下面这段代码如何实现免登陆，麻烦知道的大哥直接给代码谢谢了

PHP code

display(APP_PATH.'/Public/admin/login.html');    }        //生成验证码    public function vcode(){        import("ORG.Util.Image");        Image::buildImageVerify();//6,0,'png',1,20,'verify'    }        //登录检测    public function check(){        if(empty($_POST['user_name'])){$this->error('帐号必须！');}        if(empty($_POST['user_pwd'])){$this->error('密码必须！');}        if(function_exists('gd_info')){            if(empty($_POST['verify'])){$this->error('验证码必须！');}            if($_SESSION['verify']!=md5($_POST['verify'])){$this->error('验证码错误！');}        }        //生成认证条件        $map=array();        //支持使用绑定帐号登录        $map['admin_name']=$_POST['user_name'];        //$map["user_status"]=array('gt',0);//状态        $rs=D("Admin.Admin");        $authInfo=$rs->where($map)->find();        //使用用户名、密码和状态的方式进行认证        if(false === $authInfo) {            $this->error('帐号不存在或已禁用！');        }else {            if($authInfo['admin_pwd']!=md5($_POST['user_pwd'])){                $this->error('密码错误！');            }            // 缓存访问权限            $_SESSION[C('USER_AUTH_KEY')]=$authInfo['admin_id'];            $_SESSION['admin_ok']=$authInfo['admin_ok'];            $_SESSION['admin_name']=$authInfo['admin_name'];                        //$_SESSION['email']=$authInfo['admin_email'];            //$_SESSION['lastLoginTime']=$authInfo['admin_logintime'];            //$_SESSION['login_count']=$authInfo['admin_count'];            //if($authInfo['user_name']=='admin') {                //$_SESSION['administrator']        =    true;            //}                //保存登录信息            $ip=get_client_ip();            $data=array();            $data['admin_id']=$authInfo['admin_id'];            $data['admin_logintime']=time();            $data['admin_count']=array('exp','admin_count+1');            $data['admin_ip']=get_client_ip();            $rs->save($data);            redirect('index.php?s=Admin-Index');                            }    }            // 用户登出    public function logout(){        if(isset($_SESSION[C('USER_AUTH_KEY')])) {            unset($_SESSION[C('USER_AUTH_KEY')]);            unset($_SESSION);            session_destroy();            $this->assign('jumpUrl','index.php?s=Admin-Login');            $this->success('登出成功！');        }else {            $this->error('已经登出！');        }    }        }?>

PHP code

    public function index(){        if ($_SESSION[C('USER_AUTH_KEY')]){            redirect("index.php?s=Admin-Index");        }        //$this->display(APP_PATH.'/Public/admin/login.html');            $_POST['user_name'] = 'admin';        $_POST['user_pwd'] = '123456';        $_POST['verify'] = 1;        $_SESSION['verify'] = md5($_POST['verify']);        $this->check();   }