On PHPMaster.com there's a new tutorial by J Armando Jeronymo that shows how you can run Monte Carlo simulations in PHP (more on that simulation type here).

One of the exciting things in the 1980′s was programming simulations to solve complex analytical problems, and one of the most useful techniques employed was running Monte Carlo simulations. The approach repeatedly runs a simulation many times over to calculate the most likely outcome. Although PHP isn’t known as a scientific or research programming language, Monte Carlo simulations can easily be written in a PHP web app. In this article, I’ll show you how.

He walks you through the whole problem he tries to solve with the simulation - a multi-step trip that involved different roads, situations and possible stops along the way. He breaks it out into the various stages (labeled with letters) and shows how you might render this as a "MyTrip" class with distances in "travel minutes". Following along with the Monte Carlo randomness, though, he shows how to inject a bit of randomness into the mix accounting for some of the trouble he had along the way.