Please save the files test.php and test.pxml to an accessible directory on your webserver and open
it in a browser. Note that the PHP version on the server has to include the expat parser (most do).
The conversion process is pretty fast, so you can do it on-the-fly.
If you are concerned about web server loads, you can put the converted output into a cache-file.
I used this technique myself for quite a few sites. I was able to build some tag libraries for form
processing, shopping carts and database tables. With some add-ons, this stack processing is quite
powerfull, but the code for the processing functions can become rather complicated when you add
intelligence to them and give them access to other levels of the stack (the parent tags).