Singular Value Decomposition (SVD) in PHP

Be careful when you say "I don't care what the time limits are". SVD is an O(N^3) operation (or O(MN^2) if it's a rectangular m*n matrix) which means that you could very easily be in a situation where your problem can take a very long time. If the 100*100 case takes one minute, the 1000*1000 case would 10^3 minutes, or nearly 17 hours (and probably worse, realistically, as you're likely to be out of cache). With something like PHP, the prefactor -- the number multiplying the N^3 in order to calculate the required FLOP count, could be very, very large.

Having said that, of course it's possible to code it in PHP -- the language has the required data structures and operations.

Regarding question 1: It definitely is possible. Whether it's reasonable depends on your scenario: How big are your matrices? How often do you intend to run the code? Is it run in a web site or from the command line? If you do care about speed, I would suggest writing a simple extension that wraps calls to the GNU Scientific Library.

1. Yes. this is perfectly possible to be implemented in PHP. I don't know what the reasonable time frame for execution and how large it can compute. I would probably have to implement the algorithm to get a rought idea.

2. Yes I can help you code it. But why do you need help? Doesn't the code you wrote work?

Just as an aside question. What version of PHP do you use?