The application analyses PHP call stacks or call graphs, and is also known as a profiling tool or call graph profiler. It is predominantly for PHP, but also supports non-PHP call graphs in the callgrind format, so no PHP specifics should be included. More detail on call graph profiling can be found here:
We want an icon indicative of concepts to do with call graph profiling. Don't worry if you don't understand what it is, just see the wikipedia pages above and pull out some ideas.
Also, the following keywords may help: stack, hierarchy, statistics, instrument, performance, grind, graph, analysis. Photorealistic and 3D would be prefered but not really fussed if the result is good.