What is osCommerce? OsCommerce is an open source online shopping cart script. Using this software you can set up and operate an online store. This script handles everything from inventory management to payment processing. Being open source means that every bit of the source code is available to you, thus if any changes that you would like to make can be done by editing the PHP code. OsCommerce is considered by many to be the shopping cart that all other open source, and perhaps all other PHP based shopping cart solutions are compared to.