How to Register and Use Custom PHP Functions Inside XSL
This article is not about justifying the use of PHP inside XSL. It is about how to do so if you need to or just want to. The case that I use as an example can be done easily in XSL without the use of a PHP function.
The title stresses custom PHP functions but you can also use this approach to enable the use of built-in PHP functions. A custom PHP function must be defined and registered before it is called by an XSL page template. A built-in function only has to be registered.