On his blog recently Felix De Vliegher has posted about work he's done to gather some stats and great some data about how his PHP scripts are working based on a little statistical analysis.

Lately I've been interested in applying static analysis to PHP projects. Static analysis is the process of analysing software code - in our case PHP source code -, without actually executing the (compiled) result of the source code you’re analysing.

He mentions some types of analysis and some of the tools that can be used to measure it. He also talks about issues it can help with (like the potential for harm if a part of code is changed) and a pointer to the Pixy software he used to generate the statistics (and images like this).