AAAAGGGGHHHH... Just Realised PHP Session Variables Get Shared Between Browser Tabs!

Having built my entire booking form’s server actions based on storing values retrieved from the database in PHP Session variables, I have just found that those variables are shared between browser tabs.

I need my users to be able to have multiple booking forms open in different tabs of the same browser, and for each to work with their own unique data.

Is there any way around this, or do I just need to re-write 1000s of lines of server action steps in a way that doesn’t use PHP Sessions Variables?

Solutions that I google talk about using a PHP Session array, but I don’t have access to that concept from a Server Action!