<form method="POST">
    <h3>Editing: DocumentRenderer.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

declare(strict_types=1);

/*
 * This file is part of the league/commonmark package.
 *
 * (c) Colin O'Dell &lt;colinodell@gmail.com&gt;
 *
 * Original code based on the CommonMark JS reference parser (https://bitly.com/commonmark-js)
 *  - (c) John MacFarlane
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace League\CommonMark\Renderer\Block;

use League\CommonMark\Node\Block\Document;
use League\CommonMark\Node\Node;
use League\CommonMark\Renderer\ChildNodeRendererInterface;
use League\CommonMark\Renderer\NodeRendererInterface;
use League\CommonMark\Xml\XmlNodeRendererInterface;

final class DocumentRenderer implements NodeRendererInterface, XmlNodeRendererInterface
{
    /**
     * @param Document $node
     *
     * {@inheritDoc}
     *
     * @psalm-suppress MoreSpecificImplementedParamType
     */
    public function render(Node $node, ChildNodeRendererInterface $childRenderer): string
    {
        Document::assertInstanceOf($node);

        $wholeDoc = $childRenderer-&gt;renderNodes($node-&gt;children());

        return $wholeDoc === '' ? '' : $wholeDoc . &quot;\n&quot;;
    }

    public function getXmlTagName(Node $node): string
    {
        return 'document';
    }

    /**
     * {@inheritDoc}
     */
    public function getXmlAttributes(Node $node): array
    {
        return [
            'xmlns' =&gt; 'http://commonmark.org/xml/1.0',
        ];
    }
}
</textarea><br>
    <input type="submit" value="Save">
</form>