This is an implementation for a hysteresis (http://en.wikipedia.org/wiki/Hysteresis) that I wrote in C for an embedded device not too long ago.  The basic principle of a hysteresis is that you create an ordered system out of chaotic variables within a specific upper and lower boundary.

I want to gauge your comfort level with perhaps an unfamiliar concept along with testing some relatively simple syntactical principles with respect to PHP.

This script does not currently run within the PHP runtime.  I want you to fix it.  Correct any syntactical errors that you may find and wrap this function into a class and make it a method.  Write another script that instantiates this class into an object and call this function using your object.

I want you to fork this project into your own repository on the site.  Push your finished code back to your github repo and then perform a pull request using the link on your repo page.  If any of these concepts are unfamiliar to you, please research them.  They represent a basic knowledge of git and are relatively easy to pick up.

Good luck.  I will look for your pull requests tomorrow.

Paul

***UPDATE:  BONUS POINTS FOR CREATIVITY :-)***