In an attempt to follow some of the security guidelines for in-app purchase here: http://developer.android.com/guide/market/billing/billing_best_practices.html
I am
I've written a library for verifying Android Market licensing responses and it's available on Google Code.
It just takes a few lines of PHP to verify a license, and the formatting of keys and OpenSSL stuff is taken care of for you.
Is it possible to use cURL in your PHP script, rather than the stuff built into PHP streams. I've used them before, and have found the problems more rare, and the error messages more verbose.