[quote user="mhughes"]
I don't think it's a WTF.
I'm guessing that's an ID that the merchant can generate for
their own records. They send it along with the transaction and make a
note of it internally. Then later, if there's a transaction without
one, or with an invalid ID, the merchant can detect the fraud, not
paypal.
The response from paypal.. yeah... a wtf. But is he a paypal employee or just some moderator on some board?
[/quote]
This is exactly the problem: You're guessing that...
The snippet I included in the first post on the PayPal forum is the entirety of the documentation for that option. If it's something that PayPal want to report back to me at some stage, then I shouldn't bother with it as my session IDs aren't kept around after the session finishes. But the fact that PayPal can't, or more to the point, won't, tell me how it's used, makes it useless since I then have to make assumptions about the assumptions they've made about the meaning of this number.
Yes. The reply was from a PayPal employee.