For those of you who have ever used Microsoft Excel in a manner that required some very complicated formulas, you have probably noticed that there is a function where you can 'step in' to the formula to see in real time what data is being calculated by each function, the true value of a cell, etc. and so on.
I'm a SAP consultant by day, coder by night, and running the debug mode in SAP is very powerful. It let's you set breakpoints, see variables being populated in realtime as you step through loops, function calls, etc. in the code, and it is extremely useful for development analysis.
Are there any tools in the PHP world that would allow someone to do this kind of realtime analysis of the code execution?
Take a look at XDebug, a PHP extension.