PHP How to convert all links to have target blank

I needed to convert all links to have target blank if they didn’t already have it. I was going to go down the str_pos and str_replace etc but DOMDocument is a much quicker and easier route. See below:

function addTargetBlankToLinks($html)
{
    $dom = new DOMDocument();
    $dom->loadHtml($html);

    $xpath = new DOMXpath($dom);
    foreach ($xpath->query('//a[not(contains(@href, "protected"))]') as $node) {
        $node->setAttribute('target', '_blank');
    }

    return $dom->saveHtml();
}