PHP Conference China 2020

The WeakReference class

(PHP 7 >= 7.4.0)

Einführung

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.

Hinweis:

The class WeakReference is not to be confused with the class WeakRef of the Weakref extension.

WeakReferences cannot be serialized.

Klassenbeschreibung

WeakReference {
/* Methoden */
public __construct ( void )
public static create ( object $referent ) : WeakReference
public get ( void ) : ?object
}

WeakReference Examples

Beispiel #1 Basic WeakReference Usage

<?php
$obj 
= new stdClass;
$weakref WeakReference::create($obj);
var_dump($weakref->get());
unset(
$obj);
var_dump($weakref->get());
?>

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

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

Inhaltsverzeichnis

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User Contributed Notes 1 note

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-18
Sandor Toth
9 months ago
You might consider to use WeakReference in your Container class. Don't forget to create the object into a variable and pass the variable to WeakReference::create() otherwise you going to ->get() null.

Consider as wrong solution, which returns null
<?php
/**
* @return App
*/
public static function app() : App
{
    if (!static::
$app) {
       static::
$app = WeakReference::create(new App());
    }

    return static::
$app->get();
}
?>

Consider as GOOD solution, which returns App instance
<?php
/**
* @return App
*/
public static function app() : App
{
    if (!static::
$app) {
      
$app = new App();
       static::
$app = WeakReference::create($app);
    }

    return static::
$app->get();
}
?>
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