FYI: My company has just released I-Bill IT, a library/control that offers a rich object-model for interfacing with Authorize.net. It is written in C#/.NET, but is also callable from any COM/scripting language on Windows platforms (ASP/vbscript, PHP, etc.). There is sample code for PHP on our website.

As far as I know, it is the *only* library currently out there that supports Authorize.net's Automated Recurring Billing (ARB) feature as well as Advanced Integration Method (AIM). As I said above, it offers a rich object model over the Authorize.net services, making it much easier and faster to add such functionality to your application.

Also, we worked closely with Authorize.net during the development of the control and it is certified by them for both AIM and ARB.

Details
Download Url: http://www.itdevworks.com/download.aspx
Online documentation: http://www.itdevworks.com/Documentation/iBillit/1.0/

If you download the control without a purchased license, it will run in "trial" mode, where you can either submit payments to Authorize.net's test gateways, OR you can submit transactions to the live gateways, but in test mode. There is no timeout on the trial version.

To purchase a license, the cost is $99.00 per server/installation.

I hope this helps someone out.

David Parker
President
IT DevWorks, LLC
http://www.itdevworks.com