This program applies a PHP class that I wrote to search for a function in ALL of the WordPress files. If it finds the function, it returns the file name that it's in. The program is currently set to search files on my server, but I should have the same standard functions as anyone else who downloaded the WordPress source. This tool is a big time saver when you start hunting for a function, but don't know which WordPress file it's in.
This tool only accepts the function name. The name shouldn't be prepended with the word "function" or appended with a list of arguments enclosed in parentheses.
I created this tool quickly for my own use. It was never created with the intent to distribute to the general public. Subsequently, I have not added any form validation. If you don't understand the directions above, then you probably should be doing something else anyway. ;-)