Dom\HTMLDocument parser mangles xml:space and xml:lang attributes

[JKingweb]

Description

The following code:

<?php
$d = @\Dom\HTMLDocument::createFromString("<div></div>");
$e = $d->getElementsByTagName("div")[0];
$e->innerHTML = '<svg xml:space="default" xlink:href="about:blank" xmlns:foo="barspace"></svg>';
$svg = $d->querySelector("svg");
echo $e->innerHTML."\n";
echo $svg->attributes[0]->localName." ".var_export($svg->attributes[0]->namespaceURI, true)."\n";

Resulted in this output:

<svg space="default" xlink:href="about:blank" xmlns:foo="barspace"></svg>
space NULL

But I expected this output instead:

<svg xml:space="default" xlink:href="about:blank" xmlns:foo="barspace"></svg>
space 'http://www.w3.org/XML/1998/namespace'

Note this case is covered by the test suite here:
https://github.com/html5lib/html5lib-tests/blob/8f43b7ec8c9d02179f5f38e0ea08cb5000fb9c9e/tree-construction/webkit02.dat#L363

PHP Version

PHP 8.5.4 (cli) (built: Mar 11 2026 12:09:53) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.5.4, Copyright (c) Zend Technologies
    with Zend OPcache v8.5.4, Copyright (c), by Zend Technologies

Operating System

Arch Linux

[Oleh8978]

Reproduced on PHP 8.5.3 (CLI) built via Homebrew on macOS.

Output:

space NULL

Expected xml namespace to be preserved (xml:space with proper namespace URI).

[Oleh8978]

Reproduced on PHP 8.5.3 (CLI) built via Homebrew on macOS.

Output: space NULL

Expected xml namespace to be preserved (xml:space with proper namespace URI).

Reproduced on PHP 8.5.3 (CLI, Homebrew, macOS).

HTML parsing (Dom\HTMLDocument):

space NULL

XML parsing (DOMDocument::loadXML):
xml:space
http://www.w3.org/XML/1998/namespace

This suggests the issue is specific to Dom\HTMLDocument (HTML parsing), where the xml namespace prefix is dropped and namespaceURI is lost.