IBillIt for AIM and ARB is a single library for integrating with Authorize.net`s AIM and ARB APIs w/bonus features like line order item tracking, totaling, and custom data support. It is Authorize.net certified.
This two in one library has detailed documentation including sample code to make interfacing quite easy. Extra features include the ability to track line order items; totaling of amounts such as taxes and shipping; to include custom data; to set default properties, to avoid redundant code; duplicate billing information; and MD5 Hash Validation support. These are a great help as you would not need to develop code to support these required functions. This package has passed Authorize.Netís testing and certification process for both AIM and ARB.
Overall: An excellent piece of code that makes your development life easier when integrating a shopping cart to a standard payment processing package.