parse/collator for php

Question

I'm pretty much a newbie at php (at the "install an app and try to tweak it a bit" stage). Is there a tool anywhere which can take a script which is spread over many files and show you all the code which is processed (for a given set of arguments passed to the script) in a single output?

For example, I want to make a call to zen cart from a script in a different language, which returns a category listing without any surrounding page. So I want to be able to trace what the actual process is to generate that then strip off all the unwanted bits to create a custom script.

Answer 1

If you are looking for a debugger of some sort, have a look at XDebug or ZendDebugger.

Answer 2

What you want is called a "backwards slice" ("all the code that contributes to a specific computed result") in the computing theory literature. To compute the backward slice, something needs to parse the langauge, compute all the influences (control and dataflow) on a selected point in the program, and then display those points to you.

Slicing tools exist for langauges like C. They may exist for Java (as academic versions). I don't know of any that exist for PHP.

Another way to discover the code involved in an action is to run a test coverage tool. Such a tool marks all the code (across many files) that gets executed for a specific action (usually a "unit test" but test coverage tools really don't care). Then you simply exercise the action you care about, and look at the test coverage data. A graphical display will make it easy to see what code was executed; the part you want is buried in all the executed code. A PHP Test Coverage tool does exist and will provide nice displays of the covered code.

Answer 3

One thing I've found very helpful when looking at new / complicated codebases is to use an IDE with some sort of code intelligence. I use php eclipse, and what it does is allow you to jump into function and variable definitions either by means of hyperlinking, or popups. This can be incredibly helpful for navigating through sprawling projects because you don't have to go through all the trouble to search by hand.

In your case, with php, the best thing to do is find the entry point for a page that pulls in your list of categories. Once you find that, you can use eclipse to expand out the various function calls it makes. Being a beginner, it's very helpful to read through code in this manner, as it exposes you to lots of different ways of doing things. An additional bonus of using something like eclipse is that it provides integration with the PHP manual. So anytime you encounter a function you don't know, you can hover over, see the manual, and also how it would be used in context.