Description:
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We use SplObjectStorage to store Entities, but overwrite getHash() to prevent storing multiple objects with logically the same Entity (so "new Entity(5)" should be considered equal to another "new Entity(5)"). This works fine.

Now we considered that cloning such a list will make the offsetExists() method fail, as the test script shows. As a consequence, removeAll() will not remove anything, filter() will not filter anything, sort() will just double the number of items contained, etc.

Test script:
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class MyObjectStorage extends SplObjectStorage {
	// Overwrite getHash() with just some (working) test-method
	public function getHash($object) { return get_class($object); }
}

class TestObject {}

$list = new MyObjectStorage(); // No issues if using "new SplObjectStorage()"
$list->attach(new TestObject());

foreach($list as $x) var_dump($list->offsetExists($x)); // TRUE

$list2 = clone $list;
foreach($list2 as $x) var_dump($list2->offsetExists($x)); // FALSE

Expected result:
----------------
Both the cloned and the original list return TRUE when calling offsetExists() on a contained object.

Actual result:
--------------
Only the original list contains TRUE, while the cloned one returns FALSE.