php析构方法关于栈的问题

 1 <?php
 2 class test{
 3     var $name;
 4     var $sex;
 5     var $age;
 6 
 7     function __construct( $name, $sex ,$age )
 8     {
 9         $this->name = $name;
10         $this->sex = $sex;
11         $this->age = $age;
12     }
13 
14     function __destruct()
15     {
16         echo "再见".$this->name.‘<br>‘;
17     }
18 }
19 
20 $person1 = new test(‘张三‘,‘男‘,2000);
21 $person1 =null;
22 $person2 =new test(‘lisi‘,‘32‘,3232);
23 $person3 =new test(‘wangwu‘,‘2323232‘,222);