Search engines for searching code bases is nothing new, but this time Google did it with Google Code Search.
Obviously, it only searches "publicly accessible source code" but there is plenty of that available. Specifically, you can search within archives (.tar.gz, .tar.bz2, .tar, and .zip), CVS repositories and Subversion repositories. There are advanced restrict functions that Google allows you to use to find your code of choice, to only search PHP you can use this command, [lang:php].
Yes, there is an API for this product and you can submit your code to the index as well. Hey, search engine optimization for your code. Outsourcing firms, you may have a niche or vertical creep strategy at your finger tips here soon.