documenttype.php

См. документацию.

<?php
namespace Bitrix\Main\Web\DOM;
 
class DocumentType extends Node
{
    public function __construct()
    {
        parent::__construct();
        $this->nodeType = self::DOCUMENT_TYPE_NODE;
        $this->nodeName = '#document';
    }
 
    public function getTextContent()
    {
        return null;
    }
}