Implementation is not finished yet! But have a look at the source of PHPTAL/PreFilter.php:

http://phptal.org/files/PHPTAL-1.2.1b3.tar.gz

There's base abstract class for prefilters. Previously you had to implement interface, now you'll have to extend the class. This change allows me to add new ways of filtering in the future without any breaking changes in the interface.

The class has methods like filterDOM($node), filter($source) — you just override which ones you want. You can override all of them at once if you need, all will be called.

DOM version lets you edit PHPTAL DOM nodes after they've been parsed and edit exactly what PHPTAL "sees".

There's also filterDOMFragment($node) method. I plan to add phptal:filter="name_of_the_filter" attribute, which will let you apply filters selectively, e.g. (this is not implemented yet)

 <ul phptal:filter="remove_whitespace">
  <li>IE hates newlines in lists</li>
 </ul>

 <script phptal:filter="minify_javascript">
  etc.
 </script>

I've replaced PHPTAL→setPreFilter($filter) with PHPTAL→addPreFilter ($filter, $name = null). Yes, this means you can have any number of filters without workarounds (finally! :)

I wonder if there should be separate method for adding named prefilters for use with phptal:filter only? (e.g. you might want to make JS minification prefilter available, but you don't want to minify entire file). Currently I expect this to be handled within filter, i.e. filter would implement filterDOMFragment() only, and have filterDOM() do nothing.

Is that easy to use? Powerful enough? What do you think?