I am using the form to redirect after submission, and I am using the post submission hook to echo out a message to tell the user not to reload the page and to be patient (in case the redirect takes several seconds).
However, as expected, this makes it output that on all my forms. So I used a simple if statement to see if one of the required fields was filled in, and this fixes it.
The problem is, the inputs are named generically, so any form with the same input_# would trigger it. What is a more reliable way of filtering which form was submitted when using the post_submission hook?