Payment Module and XML?

[cmcneal]

I am trying to create a payment module and the requirement flow is as follow:
a. send request xml
b. receive response xml
c. redirect to external payment site where client enters payment info
d. payment site will redirect to my website checkout_payment and they require me to receive 2nd xml

My questions are:
a. How to redirect to external payment site (yes, the payment site has provided me the secured URL)?
b. How to receive an XML the second time around since it is not some thing I initiated?

Are there examples of this scenario?

[Kim]

Moderator's note - your 2 threads have been merged into one since they are closely related.

[cmcneal]

An Update:

I am able to fulfill all requirements except for receiving responses after redirection. But here is the summary of the flow of what I have done:

a. create an XML string
b. set cURL to pass in the XML string using the format &parm=<XML string>
c. receive the response from cURL
d. parse the response from cURL
e. use the URL specified in the response for redirection
f. redirect using PHP's header command and follow it with a die command
g. user will input the info requested in the redirected payment screen.
h. payment gateway will redirect the screen back to the client and response sent
i. Read and parse response.

It is step i, that I need assistance.

Looking forward to anyone's suggestions.