Thank you, that is helpful regarding the Merchant Defined fields. As it is, I was using the x_ shipping info to pass some data about the order. So you are saying if I use custom_arrival_date, custom_arrival_time, custom_arrival_airline, custom_arrival_flightnumber, etc., that they will get posted if I post them in my form, and they will be passed back to me in the relay response?
The SESSION this is still a little confusing to me because guess I don't understand how the redirect works. What I actually write to my page is essentially included on the page on their server.
However, I have:
session_start();
include 'config.php'; // for my database credentials
at the top of my page and later on I am inserting data into my database using what I get back from the relay response, not SESSION data, but the database INSERT is executing on my server.
$insert_row = $mysqli->query("INSERT INTO BuyerTable
(buyerFirstName, buyerLastName, buyerEmailAnet, phone, transactionID, authorizationCode, itemAmount,itemDesc,departureDate, departureTime,departureAirline,departureFlightNumber,arrivalDate,arrivalTime,arrivalAirline,arrivalFlightNumber, orderDate)
VALUES ('$buyerFirstName', '$buyerLastName','$buyerEmailAnet','$buyerPhoneAnet', '$transactionID', '$authorizationCode', '$ItemPrice', '$ItemDesc' ,'$departureDate', '$departureTime', '$departureAirline', '$departureFlightNumber', '$arrivalDate', '$arrivalTime', '$arrivalAirline', '$arrivalFlightNumber','$orderDate')");