Ordering DOMXPath query results by node-depth

Given this example document snippet:

<html xmlns="http://www.w3.org/1999/xhtml" xmlns:zuq="http://localhost/~/zuqml">
<head></head>
<body>
    <zuq:data name="a" />
    <div>
        <zuq:data name="b" />
    </div>
    <div>
        <zuq:data name="c">
            <zuq:format type="trim">
                <zuq:param name="length">300</zuq:param>
                <zuq:param name="append">
                    <span>
                        <zuq:data name="d" />
                    </span>
                </zuq:param>
            </zuq:format>
        </zuq:data>
    </div>
    <div>
        <zuq:data name="e">
            <zuq:format type="trim">
                <zuq:param name="length">300</zuq:param>
                <zuq:param name="append">
                    <span>
                        <zuq:data name="f" />
                    </span>
                </zuq:param>
            </zuq:format>
        </zuq:data>
    </div>
</body>
</html>

I'm trying to grab the <zuq:data /> nodes to manipulate, but in a certain order: deepest first.

I've currently gotten up to this point:

$nodeList = $xpath->query('.//zuq:data[not(ancestor::zuq:region)]');
foreach($nodeList as $node){
    $nodeOrder[] = Array($xpath->evaluate('count(ancestor::*)', $node) => $node->getAttribute('name'));
}

print_r($nodeOrder);

Which of course spits out this:

Array
(
[0] => Array
    (
        [2] => a
    )
[1] => Array
    (
        [3] => b
    )
[2] => Array
    (
        [3] => c
    )
[3] => Array
    (
        [7] => d
    )
[4] => Array
    (
        [3] => e
    )
[5] => Array
    (
        [7] => f
    )
)

Now I'm considering just using array_multi_sort() or usort() to order the DOMNode objects for manipulation if I were to go forward with my current 'solution'. However, it seems to me that someone might know of a more efficient way to go about this.

Any thoughts?

Note: My XPath query string is doing more than what is relevant here, for other unnecessary implementation details. I just pieced this example together from where I'm at currently.

Solution

I ended up going with usort() Manipulation of the DOM tree became increasingly complicated, so a callback function was necessary.