Understanding source code

[Lauxa]

Hi there everyone, I hope there are a few programmers out there who can relate to this question and give some advise!

I just got handed an application that is in the beginning stages of development. It is a php application based off the Zend Framework. I need to learn what is there so that I can start adding features based loosely off some design documents from a couple of years ago.

What techniques would you use to quickly digest the basic workings of a large source code base?

[ragtag]

If the code is documented or uses some auto documentation, that would be where I would start reading.

I think I would try to read it in the order it executes. Start with the index.php, see what functions it calls and so on. I've set-up a webshop using Joomla and VirtueMart, where I had to modify a lot of code and add some of my own plug-ins, but I mostly did these one at a time. Figuring out where and how the part of the code that needed fixing/modifications worked, and fixed that. Then moved on to the next problem. Eventually I began getting a little familiar with the code, how they did things and where to find stuff, but I must admit it was a rather painful experience.

[Dharma]

First figure out if it's object oriented or straight code.

If it's OO, a sweet editor like intelliJ will help wonders. You'd need a PHP plugin for it. It looks like some are in development.

Some kind of IDE/editor which helps you look through the code is best if you don't have a lot of time to inspect the code yourself.

[pokilty]

I usually play around with the system to get a feel for it. Then I look for parts that are crucial that will help me understand how things are connected. When I'm ready to look in the code, I pick a specific major feature to look out for and try to think about how I would program it. Almost every time, the way it is programmed is similar to what I envision, and so it really helps me identify key code structures pretty fast. After that, it's a matter of bouncing around to whatever interests me.