Description:
------------
I am not good at english.. 

Read the following code ..

An error occurs when you run it..
(there will be white-screen in my codes.)



Chinese :
如果你能看懂中文.那最好不过了. 上面的代码我认为__destruct被继承之后, 会导致下面两个类的对象在释放时出现无法找到static $childs的错误. 但是在我的代码里面他确实没有出现这个错误, 反而运行了很久之后出现了白屏. 看上去很像一个死循环.


Test script:
---------------
error_reporting(E_ALL);
ini_set('display_errors', 'on');

abstract class Father {
   private static $childs = array();

   public static function getChild( $child ) {
       if (!array_key_exists("$child", self::$childs)) {
           self::$childs["$child"] = new $child;
       }
       return self::$childs["$child"];
   }

   public function __destruct() {
       foreach (self::$childs as $i => $child) {
            self::$childs[$i] = $child = null;
       }
   }
}

class Child1 extends Father {}
class Child2 extends Father {}

$child1 = Father::getChild('Child1');
$child2 = Father::getChild('Child2');