I've been playing around with tempting engines a lot lately. For a recent project, I needed the ability to re-use the same template set in both JS and PHP (coupled with the History API, providing seamless dynamic behavior, yet still having raw content pages). Realistically today, there's only one choice for that sort of requirement: Mustache. I've learned a lot while playing with Mustache, and it's really changed my entire viewpoint on presentation layer construction.
He briefly gives an overview of "the past" of templating in PHP (including a mention of Smarty) and how templating tools - like Mustache - have helped to improve the situation, especially when it comes to the separation of presentation and processing. As an alternative, there's also a mention of the Twig templating engine in the comments, another popular option from the Symfony project.