Assistance Needed: Implementing 'Attach Participant to Trip' Button on Booking Website


I need some help with a solution. I am developing a booking website for our adventure trips. In my database, I have a user table, and each user can have one or more associated participants also in a table. I also have a table of trips. I would like to create a button on each trip record that allows a participant to attach themselves to a trip. It’s important to note that two participants associated with a single user might be attached to two different trips. Any suggestions on how to achieve this would be greatly appreciated.