Base on source code for the article "How To Create Barcodes in PHP" found at: http://davidscotttufts.com/2009/03/31/how-to-create-barcodes-in-php/
This script that generates barcodes in four barcode formats including Code 128, Code 39, Code 2of5, and Codabar. With a little over 100 lines of code you have the options of “vertical” or “horizontal” display, varying barcode heights, and one of four barcode formats. It does require the GD Library to be installed as a module in PHP.
Usage: <img alt="testing" src="barcode.php?text=testing" />
Result: