Weak References

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.

<?php

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

var_dump($weakref->get());
unset($obj);

var_dump($weakref->get());
// NULL

?>

Documentation

See also PHP 8.0 feature focus: Weak maps, WeakReferences

Related : References

Added in PHP 7.4