The WeakMap class

A  is map (or dictionary) that accepts objects as keys.  However, unlike the
otherwise similar , an object in a key of 
does not contribute toward the object's reference count.  That is, if at any point the only remaining reference
to an object is the key of a , the object will be garbage collected and removed
from the .  Its primary use case is for building caches of data derived from
an object that do not need to live longer than the object.

WeakMap``SplObjectStorage``WeakMap``WeakMap``WeakMap

 implements ,
 (via ),
and , so in most cases it can be used in the same fashion as an associative array.

WeakMap``ArrayAccess``Traversable``IteratorAggregate``Countable

WeakMap``ArrayAccess``Countable``IteratorAggregate

Voorbeeld: usage example

<?php
$wm = new WeakMap();

$o = new stdClass;

class A {
    public function __destruct() {
        echo "Dead!\n";
    }
}

$wm[$o] = new A;

var_dump(count($wm));
echo "Unsetting...\n";
unset($o);
echo "Done\n";
var_dump(count($wm));

int(1)
Unsetting...
Dead!
Done
int(0)

Vorige ← Superglobals Volgende WeakMap::count →

The WeakMap class

The WeakMap class

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