Brian Moon points out a simple PHP templating application shown to him - Blitz:

A coworker of mine found out about a project called Blitz. its a PHP extension that does templating. It will of course have one advantage over Smarty. Smarty is slow as its all written in PHP. PHP is slower than C and always will be. Its just life.

Tests were even done to compare it to several of the other popular templating frameworks currently offered.