Christian Stocker briefly mentions a new addition he's made to the post-PHP5.3 branching of the main trunk of the PHP development - XSLT profiling.

After PHP 5.3 was branched (for making place for - among other new stuff - namespaces), it was finally time to put my XSLT profiling addition into the official PHP sources.

The addition allows you to check in on your XSLT translations and see which spots in it are taking the most time to parse. This can be a very valuable tool when trying to see into the "black box" that PHP has around XSLT transformations. PHP 5.2ers can get the same functionality with this patch too.