<?php
$old = new stdClass();
$old->foo = 'bar';
$old->baz = &$old;

print_r($old);

$new = unserialize(serialize($old));

$new->foo = 'new';

print_r($new);
print_r($new->baz->foo);

stdClass Object
(
    [foo] => bar
    [baz] => stdClass Object
 *RECURSION*
)
stdClass Object
(
    [foo] => new
    [baz] => stdClass Object
 *RECURSION*
)
new