Description:
------------
A DOMNodeList created by evaluating a DOMXPath is not correctly traversable.
Equivalent instances of DOMNodeList created by getElementsByTagName() etc. do not have this problem.

The example below creates equivalent nodelists and shows the incorrect iteration of the one created by evaluating an XPath-expression.

Test script:
---------------
function printList(\DOMNodeList $list)
{
    foreach ($list as $outer) {
        /* @var $outer \DOMNode */
        echo 'outer: ' . $outer->nodeValue . PHP_EOL;
        foreach ($list as $inner) {
            /* @var $inner \DOMNode */
            echo ' inner: ' . $inner->nodeValue . PHP_EOL;
        }
    }
}

/**
 * @return DOMNodeList
 */
function getByXpath(\DOMDocument $dom)
{
    return (new \DOMXPath($dom))->evaluate('item');
}
/**
 * @return DOMNodeList
 */
function getByTagName(\DOMDocument $dom)
{
    return $dom->getElementsByTagName('item');
}

$xml = <<< XML
<root>
  <item>1</item>
  <item>2</item>
  <item>3</item>
</root>
XML;

$dom = new \DOMDocument;
$dom->loadXml($xml);

printList(getByTagName($dom));
echo '-------------' . PHP_EOL;
printList(getByXpath($dom));



Expected result:
----------------
outer: 1
 inner: 1
 inner: 2
 inner: 3
outer: 2
 inner: 1
 inner: 2
 inner: 3
outer: 3
 inner: 1
 inner: 2
 inner: 3
-------------
outer: 1
 inner: 1
 inner: 2
 inner: 3
outer: 2
 inner: 1
 inner: 2
 inner: 3
outer: 3
 inner: 1
 inner: 2
 inner: 3

Actual result:
--------------
outer: 1
 inner: 1
 inner: 2
 inner: 3
outer: 2
 inner: 1
 inner: 2
 inner: 3
outer: 3
 inner: 1
 inner: 2
 inner: 3
-------------
outer: 1
 inner: 1
 inner: 2
 inner: 3