PHP: parsing Markdown with sundown extension and geshi for syntax highlighting

markdown.php

<?php
require_once(__DIR__ . '/geshi.php');

class GeshiExtendedHTMLRender extends \Sundown\Render\HTML
{
    public function blockCode($code, $language)
    {
        if (!$language) {
            return '<pre><code>' . htmlspecialchars($code, NULL, 'UTF-8') . '</code></pre>';
        }
        $geshi = new GeSHi($code, $language);
        $geshi->set_language_path(__DIR__ . '/geshi/');
        $geshi->enable_classes(FALSE); // only for testing (avoid CSS)
        return $geshi->parse_code();
    }
}

$md = new \Sundown\Markdown(
    new GeshiExtendedHTMLRender,
    array('autolink' => TRUE, 'fenced_code_blocks' => TRUE, 'filter_html' => TRUE, 'no_images' => TRUE)
);
$text = 'your text here'; # copy a README.md file from a random github repository for example
echo $md->render($text);