Smarty

Smarty is a template engine for PHP. It divides the PHP as the business logic from the HTML code as the frontend logic. Generates web contents through the use of tags inside each document. It is licensed under LGPL for free use.

It is common that in big projects, the graphic designer and the developer are different people. Nevertheless, PHP tends to combine these two roles into a single developer bringing some difficulties to the process of modifying the page design since the code is all mixed up with the design. Smarty is focused on solving precisely this problem.

Smarty allows to develop templates with a great amount of functionalities such as: regular expressions while and foreach loops if, elseif, else variable modifiers - {$variable|nl2br} user defined functions math expressions evaluation

Taken from Wikipedia, February 2010