How can I track down function definitions??

Hey Everyone,
i'm a mid-level (read Junior!) PHP Developer. I'd very much like to get under the hood as much as possible. i wondering if anyone can give me advice on how I can track down, find and modify function definitions that are used through out the ZenCart framework.

I really need to do this and would sincerely appreciate help on this!,

thanks so much

Tom

Check the wiki

The majority of functions are defined in files contained in the /includes/functions/ folder. And the majority of classes are defined in files contained in the /includes/classes/ folder.

If you're using an integrated development environment (IDE) such as Aptana or Eclipse or phpStorm, you'll find that the search capability will save you tons of time and let you find the function you seek quite easily. While not really designed for PHP, Dreamweaver is almost next in line after those I just mentioned. http://www.zen-cart.com/wiki/index.php/Useful_Tools

thank you all, very helpful