Description:
------------
When doing a var_dump of a DOMNode (or one of its subclasses), the nextSibling-property does not show up. Other properties (like previousSibling) are shown as expected.

Test script:
---------------
<?php
$xmlString = '<?xml version="1.0" encoding="utf-8" ?>
<root>
</root>';

$doc = new DOMDocument();
$doc->loadXML($xmlString);
$attr = $doc->documentElement;

var_dump($attr);

Expected result:
----------------
// ... <snip> ...
  ["nextSibling"]=>
  NULL
// ... <snip> ...

Actual result:
--------------
// ... <snip> ...
// (no nextSibling)
// ... <snip> ...