PHP 8.4 classList works not correctly if copy HTMLElement by `clone` keyword.

[asika32764]

Description

The following code:

<?php
$doc = \Dom\HTMLDocument::createEmpty();
$ele1 = $doc->createElement('div');
$ele1->classList->add('foo');
$ele2 = clone $ele1;
$ele2->classList->add('bar');

echo "Element1 class: " . $ele1->getAttribute('class');
echo "\n";
echo "Element2 class: " . $ele2->getAttribute('class');

Resulted in this output:

Element1 class: foo bar
Element2 class: foo

But I expected this output instead:

Element1 class: foo
Element2 class: foo bar

3v4l.org: https://3v4l.org/eaosZ#v8.4.7

If try to clone classList will raise an error:

Fatal error: Uncaught Error: Trying to clone an uncloneable object of class Dom\TokenList

But $ele2 = $ele->cloneNode(true) works.

PHP Version

PHP 8.4.7 (cli) (built: May  6 2025 14:14:22) (NTS Visual C++ 2022 x64)
Copyright (c) The PHP Group
Zend Engine v4.4.7, Copyright (c) Zend Technologie

Operating System

Windows 11 and 3v4l.org

[nielsdos]

Good find.

Some clarification as to why cloneNode behaves correctly but clone does not:
clone creates a copy of the entire object, while cloneNode only copies the tree structure and then creates a new object instance. This is significant if you have custom properties on an Element instance, or you extend the Element class yourself.

The reason why TokenList is uncloneable is because the DOM spec requires it to always be the same object for a single Element. Therefore, the class can't be cloneable as it would violate this constraint.