I wrote a simple virtual machine in PHP tonight, for the heck of it. Here’s an excerpt from my information page, you can read more here.

The PHP Virtual Machine is a basic virtual machine written in PHP that accepts a set of instructions modeled loosely in the style of assembly, then executes them. In this first stage it has a 512 integer “RAM” and accepts 7 unique instructions. It also has to have the program coded directly into the script, as I haven’t finished the input side of things yet.