Twig Function to get the file mtime in template for HTTP Caching

twig_file_date_extension.php

<?php

$function_filedate = new Twig_SimpleFunction(
    'fileDate',

    /**
     * @param $file_path
     * This function generates a new file path with the last date of filechange
     * to support better better client caching via Expires header:
     * i.e:
     * css/style.css -> css/style.1428423235.css
     *
	 * Usage in template files:
	 * i.e:
	 * <link rel="stylesheet" href="{{ fileDate('css/style.css') }}">
	 *
     * Apache Rewrite Rule:
     *
     * RewriteCond %{REQUEST_FILENAME} !-f
     * RewriteCond %{REQUEST_FILENAME} !-d
     * RewriteRule ^(.*)\.[\d]{10}\.(css|js)$ $1.$2 [NC,L]
     *
     * Apache Document Root MUST be configured without the trailing slash!
     *
     * @return mixed
     */
    function ($file_path) {
        $change_date = @filemtime($_SERVER['DOCUMENT_ROOT'].'/'.$file_path);
        if (!$change_date) {
            //Fallback if mtime could not be found:
            $change_date = mktime(0, 0, 0, date('m'), date('d'), date('Y'));
        }

        return preg_replace('{\\.([^./]+)$}', ".$change_date.\$1", $file_path);
    }
);

$twig->addFunction($function_filedate);