I'm currently working on a statistical forecast component for airports
which is programmed in PHP, there are different forecast methods like
projection, exponential smoothing, time-, macro and multiple macro
regression. For the latter ones I need to do some further statistical
testing including the so called "t-test" and "f-test":

http://en.wikipedia.org/wiki/T-test
http://en.wikipedia.org/wiki/F-test

I don't want to implement these tests by myself for I'm sure there
have to be some mathematical and/or statistical libraries out there
which provide these methods and functions and can be used and included
into my project under some open source OR commercial license (doesn't matter).

These libraries HAVE to be written in PHP because I canīt include
other external applications into my PHP application due to server-side
technical limitations!

So applications like the R-System (http://www.r-project.org/) or
comparable applications in any compiled or interpreted language other
than PHP are not useful for my purposes.

My question in short:

Are there any free or commercial mathematical /
statistical _PHP_ libraries / packages / class collections for doing
the t- and f-tests and/or any other forecast methods listed above? If
not, are there any detailed instructions available on how to implement
these functions in a programming language like PHP without being a
math ace ;-) ?