So here is the end result functionality, that I need to happen:

1. user completes form
2. user gets email and in that email is a link
3. the link is a custom link (ie. the URL is dynamically made, where I have a unique number in the URL)
4. the point of the unique number in the URL is so when the user clicks that link, the URL triggers  my PHP script and I know who clicked the link and I can proceed with my logic.

typically I would create PHP scripts to do all this and I created the HTML forms all custom... BUT since using FF, I'm wondering, thinking there is an easier, faster way to use FF? example: I use a hidden form field to create the unique number.
Then somehow create a field or link to have inserted in the confirmation email (which can already be sent). my issue or not understanding... is using the webhooks the only way to add in PHP code? OR is there field or way to add in PHP code to a field, so not needing the webhooks?   thanks!