PHP Getting parent's ID => child's value as array from XML

Question

I have an XML file structured like this

<serieslist>
    <series sid="123">
        <title type="main">Series 123 Main Title</title>
        <title type="official">Series 123 Official Title</title>
        <title type="short">S 123</title>
    </series>
    <series sid="456">
        <title type="main">Series 456 Main Title</title>
        <title type="official">Series 456 Official Title</title>
        <title type="short">S 456</title>
    </series>
    /* +6000 more <series> nodes */
</serieslist>

I need to make an associative array that consists of the "sid" attributes and main series titles like this

array(
    123 => "Series 123 Main Title",
    456 => "Series 456 Main Title",
    //...
);

I tried using this xpath query //series/title[@type="main"] and I get the nodelist

$xml = DOMDocument::load('serieslist.xml');
$xpath = new DOMXPath($xml);
$titles = $xpath->query('//series/title[@type="main"]');
$series = array();
foreach($titles as $title) {
    $series[] = $title->nodeValue;
}

Results in

$series = array(
    0 => "Series 123 Main Title",
    1 => "Series 456 Main Title",
    //...
);

But I need parent's "sid" attribute too. How could I do that in a non-resource-intensive way?

Answer 1

Quite simple. Just reference the parent node to $title :

foreach($titles as $title) {
    $id = $title->parentNode->getAttribute('sid');
    $series[$id] = $title->nodeValue;
}