I hate PHP and don't even want to talk about it but I did skim through the docs for Smarty. The rationale is that PHP sucks as a template engine, so why not create a new one and use PHP for the model-controller/whatever.

Maybe that seems perverse, but you have stuff like Node.js in existence that oddly enough solves some problems quite nicely, so maybe it works for PHP guys. I'll never see the appeal compared to other languages though.

edit: That being said, the final result looks kind of horrible to me.