There is a tutorial for Google Wallet in their documentation involving PHP. Their sample code works and is easily modified to use in a test/production environment. Keep in mind that you do have to change several elements when going from sandbox to production. Do not assume you keys and ID's will be the same in both environments as they will not.
Settings page: checkout.google.com/inapp/merchant/settings.html
Sample code and documentation (limited explanation, but if you know PHP, no problem):
https://developers.google.com/commerce/wallet/digital/docs/
code.google.com/p/iap-php/source/browse