\Dom\ParentNode::querySelector and \Dom\ParentNode::querySelectorAll requires elements in $selectors to be lowercase #20395

Description

(Related: #17802 - in this issue there was a very similar issue, where if attribute names in $selectors didn't match the case of the attribute then the node was not matched.)

The following code:

<?php
$html   = "<!doctype html><html><head></head><body></body></html>";
$dom    = \Dom\HtmlDocument::createFromString($html);
var_dump(\is_null($dom->querySelector("html")));
var_dump(\is_null($dom->querySelector("Html")));
var_dump(\is_null($dom->querySelector("HTML")));

Resulted in this output:

bool(false)
bool(true)
bool(true)

But I expected this output instead:

bool(false)
bool(false)
bool(false)

PHP Version

All PHP8.4 versions and git.master (2025-09-27)

Operating System

No response