Thank you sooooo much for posting this example. After two weeks of off and on struggles with Authroize.net's sample php code without success, I plugged John's sample code in and within 5 minutes I had tested successfully with my developers account. After another 15 minutes, I had this solution implemented on my site and have tested two transactions of my own, without fail!!

Thanks for the post.

Sam

P.S. The godaddy code is an important piece if you are hosted on godaddy. Don't forget that!