<?php
namespace app\admin\common;
use think\Controller;
use think\Session;
class Base extends Controller
{
protected function _initializa()
{
parent::_initializa();
//在公共控制器的初始化方法中，创建一个常量来判断用户是否登录或已登录
define('USER_ID',Session::get('user_id'));
}
//判断用户是否登录,在后台
protected function islogin()
{
//如果登录常量为null，表示没有登录
if (is_null('USER_ID')) {
$this -> error('未登录，无权访问！','login/index');
}
}
//如果用户已经登录，将不允许再次登录
protected function alreadyLogin()
{
//如果登录常量为null，表示没有登录
if (!is_null(USER_ID)) {
$this -> error('已经登录,不要重复登录~~', 'index/index');
}
}
}When accessing the background, it prompts the undefined constant USER_ID,
Logically speaking, it is in front define('USER_ID',Session::get('user_id')) ; The constant has already been defined. Why is this prompt
