Best practice of developing callbacks with a third-party payment gateway?

[spike_joseph]

Hey everyone,

I'm working on a Stripe Checkout payment gateway, where when someone places an order, it takes them to the Stripe hosted Checkout page to make the payment.

I have a few concerns and I'm not sure if I'm doing it right.

The flow chart I attached is how it works, and at following points:

• Point A: When our backend gets a success/cancel callback from Stripe, it redirects the user to the gateway callback page (https://example.com/modules/gateways/callback/stripecheckout.php) with all the necessary params in the URL.
• Point B: On the callback page, I do another redirect (header("Location: https://example.com/cart.php?a=complete");) to a hard-coded "Order Confirmation" page URL.

Here are my questions:

• Point A: Is it okay to include all the params in the URL for the redirect? Or should I use a POST request instead?
• Point B: In the sample code, I didn't see any redirect code. Is it alright to use a hard-coded URL for the redirect? And what happens if a user places multiple orders at once?

Thanks!

[spike_joseph]

Update:

For those who has the same question, just redirect to the viewinvoice.php page with proper invoice ID is all.