Description:
------------
There is a mistake in the documentation of ArrayIterator::unserialize about the return type.
It should be void instead of string.

The 'Return Values' should also be updated accordingly.

See: https://www.php.net/manual/en/arrayiterator.unserialize.php

Test script:
---------------
<?php
$a = new ArrayIterator();
var_dump($a->unserialize(
    (new ArrayIterator([1, 2, 3]))->serialize()
));
foreach ($a as $e) {
    var_dump($e);
}

Expected result:
----------------
NULL
int(1)
int(2)
int(3)