I'm adding links to the two most popular php profiling tools because I've had mixed results with both. If one is giving you seg faults, try the other. Both generate files that can be read by [http://kcachegrind.sourceforge.net/cgi-bin/show.cgi KcacheGrind] - a good tool for visualizing the data. Otherwise they both have command line utilities as well.
==Load Testing==
ToDoThat