The example Kirk provided is not the best option, there's a method "removeAll" that you can pass the SplObjectStore itself, and as the name says, remove all stored objects.
(PHP 5 >= 5.3.6, PHP 7)
SplObjectStorage::removeAllExcept — Removes all objects except for those contained in another storage from the current storage
Removes all objects except for those contained in another storage from the current storage.
storageThe storage containing the elements to retain in the current storage.
No value is returned.
Example #1 SplObjectStorage::removeAllExcept() example
<?php
$a = (object) 'a';
$b = (object) 'b';
$c = (object) 'c';
$foo = new SplObjectStorage;
$foo->attach($a);
$foo->attach($b);
$bar = new SplObjectStorage;
$bar->attach($b);
$bar->attach($c);
$foo->removeAllExcept($bar);
var_dump($foo->contains($a));
var_dump($foo->contains($b));
?>
The above example will output something similar to:
bool(false) bool(true)
The example Kirk provided is not the best option, there's a method "removeAll" that you can pass the SplObjectStore itself, and as the name says, remove all stored objects.
You may remove all elements by passing empty SplObjectStorage
$splStorage->removeAllExcept(new SplObjectStorage());