I'm in no way associated with this product...
But in my search for a good template engine, I tried them all, and I love Smarty. It's quick, easy, and logical. There is a great discussion group that you can find about in the docs. The developers (Monte Ohrt & Andrei Zmievski, recoginize him? One of the developers of PHP) improve the template all the time.
If you don't know what a template it, it allows you to separate your program logic from the html layout. Now before, I tried this with the other engines and I never got it to work right... I always had this goal of developing the layout of my site in Dreamweaver, but have the code elsewhere.... With Smarty it works great, when I look at the layout in Dream Weaver I see pretty much what the site will looklike with placeholders for the ultimate values which will be provided by the Templete, and for the same page I have a matching .php file, it's a pleasure to look at this file and only see php code, it makes it so much easier to see what I was trying to do, without all the html stuff in there....
Here is a blurb from anothe web site about it:
"Smarty is a template engine for PHP. One of the unique aspects about Smarty that sets it apart from other templating solutions is that it compiles the templates into native PHP scripts upon the first invocation. After that, it merely executes the compiled PHP scripts. Therefore, there is no costly template file parsing for each request."
oh.. and of course it's free....
The only reason I'm posting this, is because I've never seen a reference to it on phpbuilder, and it has easily tripled my productivity (and allows me to easily have someone else do the layout if I want, and that person doesn't need to know php at all)
You can check it out here:
http://www.phpinsider.com/php/code/Smarty/