You got me on that one. I didn't find much for PHP out on google or hotscripts.com. But like I said, Perl has a beautiful XLS library which I find runs pretty quick. I just had PHP interface with Perl and life was good.
Its all about using the right tool for the right job. Instead of using a hammer to take down a tree, I found a chain saw.
If you're still stuck on PHP, you may have to build your own XLS reading library.