[php-src] Issue #20281: \Dom\Document::getElementById() is inconsistent after nodes are removed

Issue: https://github.com/php/php-src/issues/20281 Author: cscott ### Description The following code: ```php <?php $d = \Dom\HTMLDocument::createFromString('<p id="a">b</p><p id="a">c</p>'); $p = $d->getElementById('a'); $p->remove(); echo($d->getElementById('a')->innerHTML); ``` Resulted in this output: ``` Attempt to read property "innerHTML" on null ``` But I expected this output instead: ``` c ``` Compare to the following JS code in a browser: ```javascript > document.body.innerHTML = '<p id=a>b</p><p id=a>c</p>' '<p id=a>b</p><p id=a>c</p>' > p = document.getElementById('a') <p id=​"a">​b​</p>​ > p.remove() undefined > document.getElementById('a').innerHTML 'c' ``` ### PHP Version ```plain 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 _No response_