I have to do one project for my thesis involving Artificial intelligence, collaborative filtering and machine learning methods.
I only know PHP/mysq/JS, and there is not
I believe Python is nice for this sort of tasks because of it's flexibility. Using the numpy/scipy libraries together with a nice plotting lib (chaco or matplotlib for instance) makes the workflow of working with the data and algorithms easy and you can lab around with the code in the live interpreter in an almost matlab-like manner. Change a line of code here, cleanse the data there and watch the whole thing live in a graph window without having to bother with recompilation etc.
Once you settled on the algorithms it is fairly easy to profile the code and move hotspots into C/C++ or Fortran for instance if you are worried about performance.
(you could even write the stuff in Jython and drop down into java for the performance-heavy bits of the code if you really like to be on the JVM platform)
Pretty much any language can be used to code pretty much anything - given the effort and will. But Python has more functional programming constructs which may be more useful when you are coding AI.
You can use either Java or Python. A lot of resources are available for both languages.
I think following books might suit for your purpose.
Programming collective intelligence: building smart web 2.0
collective intelligence in action