Google Merchant API automation with PHP

[GoTTsProfeT]

I have up until recently used the paypal IPN to process transactions automatically and generate serial keys/send emails to my buyers.

 

PayPal's IPN is pretty straight forward, with POST variables, and authentication by sending back the request to verify its legit.

 

However, I began looking through the google API code to be able to do this, and it appears to use XML in which I am knowledgless and have no idea how to parse and take action off of.

 

If someone could please show me how to parse this XML and take action off it, AND verify it with google, in PHP, I would much appreciate it.