openPlaG 1.01

openPlaG is an online function graph plotter, written in PHP. This application can compute and plot a very high amount of functions, including many probability functions and is fairly good configurable.
Instructions:
To run the program, youll need access to a web server with PHP 4 or 5 and GDlib running. I dont know with which PHP4 versions it works, but at least with 4.4.1 it does. For lower versions just try it out.
The downloaded program is a zipped tarball, which contains these files:
- function.php the iframe content where the graph (png-image) is shown.
- gnu_gpl.txt GNU GENERAL PUBLIC LICENSE Version 2. Read it, dont change it.
- graph.css the used style sheet. This is very minimalistic.
- graph.php calculates the graph and draws the image.
- init.php security check and formulae (functions) definitions.
- instructions.html explains the use of the plotter.
- openPlaG.html start here when getting into the source code. This is the start page with the two iframes for the graph and the single value. You may want to change its name to index.html or something like that.
- single.php calculates a formula with a single value, not the whole graph. The result is shown in the second iframe.
Upload the files on your server. The program should work without problems, if server and PHP are configured properly. Make your changes as you want to, but dont forget to tell me if you make something really amazing or useful.