用thinkphp操作session

写了一段代码，对session进行一些常用的操作：

<?php
namespace Home\Controller;
use Think\Controller;

class Demo1Controller extends Controller {
    public function index(){
        $user = M("city")->select();

        $this->assign(‘list‘,$user);

        $this->display();
    }

    //session赋值
    public function test1() {
        session(‘username‘,‘admin‘);
        session(‘useralias‘,‘管理员‘);

        echo ‘session赋值‘;
    }

    //session取值
    public function test2() {
        echo ‘session取值<br />‘;
        echo ‘username：‘.session(‘username‘).‘<br/>‘;
        echo ‘useralias：‘.session(‘useralias‘).‘<br/>‘;
    }

    //删除session
    public function test3() {
        session(‘username‘,null);
        session(‘useralias‘,null);

        echo ‘删除session‘;
    }

    //判断session是否存在
    public function test4() {
        if(session(‘?username‘)) {
            echo ‘username存在<br/>‘;
        } else {
            echo ‘username不存在<br/>‘;
        }

        if(session(‘?useralias‘)) {
            echo ‘useralias存在‘;
        } else {
            echo ‘useralias不存在‘;
        }
    }
}