I'm looking for some advice in regards to how I approach dealing with a redirected URL with params.

I have a client, let's say Client #A.

They have a WordPress website we previously created with WooCommerce, custom theme, Realex integration (SkyVerge). They sell delivery/packing materials.

Third Party Service #B provides quoting service for users on their #B website for users. (For removals quotes). I can't control what they do as they are upstream (I'm not sure if this is the right terminology?).

So the user is on TPS#B's website entering their details, they hit 'finalise' and TPS#B provide a URL redirect from their website loaded with parameters like so:

;first_name=John&last_name=Doe&total=465.6

The intention is once they get redirected to client website #A, given the URL (as above) I grab the values, (possibly populating a form) user reviews the price, clicks buy now. They then get sent to Realex to do the hosted payment much like WooCommerce already does etc. *1 *2

My main query is around the first stages. I can't shake the nagging feeling there is a better way to do this... Have I got the approach correct? To be honest, I'm a bit confused, maybe overthinking it. Is creating a payment page with some kind of form that pulls from the URL even a good idea? I know an API would be better but they don't offer that option.

I considered using WooCommerce somewhere within this process but the problem is the price is going to vary from user to user. Therefore I don't think it's possible to 'create a product' every time. (I mean maybe it would be a good idea since I could use the already existing Realex integration.)

I'd appreciate any help even if it's just guidance on how to get started or if there are any thoughts on the best way to handle this situation.

Points raised

*(1. Why doesn't TPS#B just forward to Realex? I don't think that's possible, this is why they have given me the URL.

*(2. I'm going to have to create a payment gateway for this along with some kind of rudimentary order system (a bit like WooCommerce but more basic). I understand this part as I can see the theory behind it.