I am testing payment providers (to sell software), and I've seen that both e-junkie and SWREG work in a similar way about the key generator. I am referring to a key generator like Armadillo (but it's hosted in my site).
This is how it works:
1- The payment provider server sends to my online keycode program a list of strings (data about a specific purchase).
2- There is a PHP page in my sites that captures this data.
3- After that, my key generator is executed and the output will be a customer's key license.
4- The payment provider captures this key license (sent to console) and embed it into the receipt email the customer receives.
So what's the PHP function I must use to send the result (the generated key) back to the payment provider's server? I'm not sure if it's a simple "echo" or I must use something like "curl".
Any hint will be very appreciated.