(PHP 8 >= 8.4.0)
Dom\TokenList::add — Adds the given tokens to the list
   Adds the given tokens to the list, but not any that
   were already present.
  
tokens没有返回值。
Dom\SYNTAX_ERR
   的 Dom\DOMException。
  
 Dom\INVALID_CHARACTER_ERR
   的 Dom\DOMException。
  
 示例 #1 Dom\TokenList::add() example
Adds two classes to a newly created paragraph element.
<?php
$dom = Dom\HTMLDocument::createEmpty();
$p = $dom->createElement('p');
$classList = $p->classList;
$classList->add('font-bold', 'important');
echo $dom->saveHtml($p);
?>以上示例会输出:
<p class="font-bold important"></p>
