php-stl is a templating implementation similar to java's JSTL.
This is a tag-based template engine with configurable classes to
handle various tags. The templates are written in XML, which differs
from the JSTL, but provides clean output.

Note that php-stl now provides its own template handling, and can
still piggyback on either PHPSavant (http://phpsavant.com) or
Smarty (http://smarty.php.net/) as a compiler. Note also that php-stl
is designed for PHP 5, though a PHP 4 implementation wouldn't be
difficult. 

Check out the wiki at http://php-stl.redtreesystems.com or source forge at http://sourceforge.net/project/php-stl.