The WeakReference class

(PHP 7 >= 7.4.0, PHP 8)

Introduction

Weak references allow the programmer to retain a reference to an object which does not prevent 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 class WeakReference {
/* Methods */
public __construct()
public static create(object $object): WeakReference
public get(): ?object
}

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

VersionDescription
8.4.0The output of WeakReference::__debugInfo() now includes the referenced object, or NULL if the reference is no longer valid.

Table of Contents