[Weakref :: acquire](https://www.php.net/manual/en/weakref.acquire.php)—获取对该对象的强引用 [Weakref :: \_\_ construct](https://www.php.net/manual/en/weakref.construct.php)—构造一个新的弱引用 [Weakref :: get](https://www.php.net/manual/en/weakref.get.php)—返回弱引用指向的对象 [Weakref :: release](https://www.php.net/manual/en/weakref.release.php)—释放以前获取的参考 [Weakref :: valid](https://www.php.net/manual/en/weakref.valid.php)—检查所引用的对象是否仍然存在