Is it possible to somehow resume a User Session later in PHP?

General questions
1

We have the following scenario:

  • User browses the shop
  • Adds some products to the cart
  • User places an order, but this is is not yet payed

Everything is tracked as one visit. Then some external steps happens

  • The order is payed later in the PHP backend (so no Browser/Session)
  • The PHP Backend will track an eCommerceOrder

Is it possible to “find” and resume the user session somehow, so that everything is together? We currently don’t use _id nor uid as far as I can see.