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, PHP 8)
SplObjectStorage::removeAllExcept — Remove todos os objetos, exceto aqueles contidos em outro armazenamento, do armazenamento atual
Remove todos os objetos, exceto aqueles contidos em outro armazenamento, do armazenamento atual.
storage
O armazenamento contendo os elementos a serem retidos no armazenamento atual.
Retorna o número de objetos restantes.
Exemplo #1 Exemplo de SplObjectStorage::removeAllExcept()
<?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));
?>
O exemplo acima produzirá algo semelhante a:
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());