Description

The following code:

<?php
$d = \Dom\HTMLDocument::createFromString('<p id="a">b</p><p id="a">c</p>');
$df = $d->createDocumentFragment();
$df->getElementById('a');

Resulted in this output:

  Error  Call to undefined method Dom\DocumentFragment::getElementById().

But I expected this output instead:

(no output)

This method is present in the DOM spec: https://developer.mozilla.org/en-US/docs/Web/API/DocumentFragment/getElementById and the similar method ::querySelector is implemented; I can't tell if querySelector actually uses the ID index though or does a linear scan through the fragment. (Aka, this method should not just be implemented, it is expected to have O(1) performance.)

PHP Version

PHP 8.4.13 (cli) (built: Oct  1 2025 20:34:15) (NTS)
Copyright (c) The PHP Group
Built by Debian
Zend Engine v4.4.13, Copyright (c) Zend Technologies
    with Zend OPcache v8.4.13, Copyright (c), by Zend Technologies

Operating System

Ubuntu 24.04.1