SharePoint Search can also crawl a normal website or php sites. If you’re using a wiki which is based on php, you can also add it in your search index. But after you prepared everything like the authentification, you should also be aware that urls maybe case sensitive. If you do not pay attention you might get the following error:
The URL was permanently moved. ( URL redirected to http://site/pages/home.aspx)
I’ve found the solution in this post. You just add a crawl rule in the central administration. In the crawl rule you have to activate the checkbox for “Match Case”. After that do a full crawl and it should work.
Hope it helps you.