Paul Meagher over at PHPMath has posted some interesting information about some code that deals with some of PHP's special math functions.

I have not ported all the gamma functions in this library, nor have I ported the chebyshev, airy and bessel functions. I only ported the ones I had an immediate need for. It would be nice to port the rest and perhaps see if there is a better approach to porting this class then the one I took. Note that the term "Special" is often used technically to refer to these functions, and is not being used for lack of a better term.

So in the intrests of PHP and math, head on over to PHPMath and check it out!