SplObjectStorage class can be nicely used in Observer pattern, for example:
<?php
class Subject implements \SplSubject
{
private $observers;
public function __construct()
{
$this->observers = new \SplObjectStorage;
}
public function attach(\SplObserver $observer)
{
$this->observers->attach($observer);
}
public function detach(\SplObserver $observer)
{
$this->observers->detach($observer);
}
public function notify()
{
foreach ($this->observers as $observer) {
$observer->update($this);
}
}
}
?>