So, I am not sure of the best way to go about this, sounds like htaccess may be the way to go though I am not super strong in that area. Basically, this is for a SAAS setup so the user can move on to step 2 and create their profile on the software after payment is made, the scenario would go something like this:
(Step 1 - A) The user completes their subscription payment on the primary website and receives a special access link to continue to (Step 2 - B). However, I would like to disallow any access to B, and only allow it if the user is coming from the specified URL/Page A
It should be noted that, the front-end of the website for A is domain .com and the profile/Setup side for B is subdomain. domain .com/user/register.
Ideally, after a user makes payment, I would like to provide them with a link via email as well as a use a special button on the success page that both take the user to B.
Any suggestions would be great!