Predefined Interfaces and Classes
PHP Manual

The WeakReference class

Introduction

Weak references allow the programmer to retain a reference to an object without preventing the object from being destroyed. They are useful for implementing cache-like structures. If the original object has been destroyed, null will be returned when calling the WeakReference::get method. The original object will be destroyed when the refcount for it drops to zero; creating weak references does not increase the refcount of the object being referenced.

WeakReferences cannot be serialized.

Class synopsis

final WeakReference
/* Methods */
public __construct()
public static WeakReference create(object $object)
public objectnull get()

WeakReference Examples

Example #1 Basic WeakReference Usage

<?php

$obj = new stdClass();
$weakref = WeakReference::create($obj);

var_dump($weakref->get());

unset($obj);

var_dump($weakref->get());

?>

The above example will output something similar to:

object(stdClass)#1 (0) {
}
NULL

Changelog

Version Description
8.4.0 The output of WeakReference::__debugInfo now includes the referenced object, or null if the reference is no longer valid.
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