Plates, the native PHP template system that's fast, easy to use and easy to extend.
Plates templates are just plain PHP files, you only need to know one language. The language you already use, PHP.
Plates works in any PHP project, be it a CLI app or a CMS. You can use it for emails and for HTML files, it is just PHP.
You need additional functionality? Just add it, Plates has a rich extension system.