Filesystem::extension PHP Method

    public static function extension($file)
    {
        $extension = pathinfo(strtolower($file), PATHINFO_EXTENSION);
        if ($extension) {
            return $extension;
        }
    }

 protected function filename($filename)
 {
     if (is_null(Filesystem::extension($filename))) {
         $filename .= '.htm';
     }
     return $filename . '.php';
 }