DOMXML crash at end of script execution when there is loaded XML document containing reference to entity, which contains reference to another entity in its substitute text. 

Here is small example to reproduce this bug:

<?php
$xml = '<?xml version="1.0"?>
<!DOCTYPE root [
<!ENTITY ent1 "some">
<!ENTITY ent2 "&ent1; text">
]>
<root>&ent1;</root>';

$xml = xmldoc($xml);
?>