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
class LoginAction extends BaseAction{
    //默认操作
    public function index(){
if ($_SESSION[C('USER_AUTH_KEY')]){
redirect("index.php?s=Admin-Index");
}
$this->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！');
        }
    }
}
?>