Blockchain.info Payment API -> Callback gets a 302?
normally it has to be 200, the 302 mean that the requested resource resides temporarily under a different URI.

Dont block "GET" requests on your code because blockchain use GET method to send your notifications about the transactions.

Use your full domain name including the leading www example : 

http://www.example.com/callback....

In case of https ! make sure you include it in the callback URL.