<?php

 class Admin {

     public function __construct() {

         if($this->top === null) {

             return;

         }

         $this->toper = new $this->top();//属性加了圆括号变成了方法（属性值->值->方法）

     }

     public function proc($danger) {

         if($danger <= $this->power) { //如果权限能解决，就解决，这里也不会出现大权限解决小问题，因为我们是从最低级的版主一层层往上走的

             $this->doProc();

         } else {

             $this->toper->proc($danger);

         }

     }

 }

 class Banzhu extends Admin {

     protected $power = 1;

     protected $top = 'Police';

     protected function doProc() {

             echo '删帖';

     }

 }

 class Police extends Admin {

     protected $power = 2;

     protected $top = 'Guoan';

     public function doProc() {

         echo '抓人';

     }

 }

 class Guoan extends Admin {

     protected $power = 3;

     protected $top = null;

     public function doProc() {

         echo '灭口';

     }

 }

 $danger = 3;

 $admin = new Banzhu(); //不合适的帖子肯定是版主最先发现，所以这里是new的版主

 $admin->proc($danger);

 print_r($admin);