Description

The following code:

<?php
$d = new \DOMDocument();
$d->appendChild($d->createElement('root'));
$d->createAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns');

Resulted in this output:

PHP Fatal error:  Uncaught DOMException: Namespace Error

But I expected this output instead:
N/A

The first step of the DOM specification for createElementNS is:

1. Let namespace, prefix, and localName be the result of passing namespace and qualifiedName to validate and extract.

The validate and extract section has the following steps:

6. If prefix is non-null and namespace is null, then throw a "NamespaceError" DOMException.
7. If prefix is "xml" and namespace is not the XML namespace, then throw a "NamespaceError" DOMException.
8. If either qualifiedName or prefix is "xmlns" and namespace is not the XMLNS namespace, then throw a "NamespaceError" DOMException.
9. If namespace is the XMLNS namespace and neither qualifiedName nor prefix is "xmlns", then throw a "NamespaceError" DOMException.

The namespace is the XMLNS namespace, and the qualifiedName is "xmlns", so it shouldn't be throwing a DOMException. PHP 8.2.x doesn't throw the DOMException. My system has libxml 2.12.1.

PHP Version

PHP 8.3.0

Operating System

macOS 13.4.1