How to add an attribute with a value to a tag using the DOMDocument class?

Question

PHP

Tried using setAttribute method - doesn't help

$dom->loadHtml($html);
$h2s = $dom->getElementsByTagName('h2');
foreach ($h2s as $h2) {
    $h2->setAttribute('id', 5);
}

Answer 1

Where do you expect to see it?
The method adds an attribute to the object, from which you then need to build html again.