exclude List for Sitemap

[Gummibeer]

I added another Var to exclude folders from the Sitemap, for example: slider, home-parts, search
And added the <lastmod> Attribute.

class Pico_Sitemap {
    private $is_sitemap;
    private $exclude;

public function __construct(){
    $this->is_sitemap = false;
    $this->exclude = array('home', 'slider', 'suche');
}

public function get_pages(&$pages, &$current_page, &$prev_page, &$next_page) {
    if($this->is_sitemap) {
        global $config;
        header($_SERVER['SERVER_PROTOCOL'].' 200 OK');
        header('Content-Type: application/xml; charset=UTF-8');
        $xml = '<?xml version="1.0" encoding="UTF-8"?><urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">';
        foreach( $pages as $page ) {
            preg_match('/\/('.implode('|', $this->exclude).')\//', $page['url'].'/', $matches);
            if(empty($matches)) {
                $index = '';
                $date = '';
                $path = realpath(dirname(__FILE__)).DIRECTORY_SEPARATOR.'..'.DIRECTORY_SEPARATOR.'content'.DIRECTORY_SEPARATOR.str_ireplace($config['base_url'], '', $page['url']);
                if(is_dir($path)) { $index = 'index'; }
                $file = realpath($path.$index.'.md');
                if(file_exists($file)) { $date = date ("Y-m-d", filemtime($file)); }
                $xml .= '<url><loc>'.$page['url'].'</loc><lastmod>'.$date.'</lastmod></url>';
            }
        }   
        $xml .= '</urlset>';
        header('Content-Type: text/xml');
        die($xml);
    }
}