Please excuse if I'm posting in the wrong thread, or if this has been asked before. I'm a new here and am having difficulty finding an answer to my situation, as follows:
I'm currently in Test Phase 1, and am using SIM relay response to authorize and capture transactions. The name of relay page is receipt.php, and all seems to work well.
However, how to make sure that this receipt.php be POST-ed and grabbed ONLY BY Authorize.net and not someone else? I was thinking to check $_SERVER but then surely there is an API to do this? Or... is this what isAuthorizeNet() is for?