I’m surprised that this article didn’t talk about doing regression analysis with PHP and R. Using R adds a dependency, but it might be worth it. I’d recommend this article[1] if you’re interested; the “cat file.txt | /usr/bin/R --vanilla” line is particularly helpful in executing R directly from PHP.

[1] https://www.stanford.edu/~mjockers/cgi-bin/drupal/node/25

That's how I do things, too. But for the purposes of understanding the underlying math, I found this code rather useful.

Do you have similar regression code in Matlab?

Very useful. Thanks for sharing carbocation.