Creating a multi-page PHP form with sessions

[Rich777]

I need to create a pretty extensive form with PHP/MySQL with a lot of conditional logic that ultimately ends with submission to the MySQL database. So basically the user makes their first choice with a radio button (has to be because they are "choosing" pictures) and then gets taken to the next "page" of the form based on that submission. That submission ALSO has to be stored in a session or cookie because at the end of the form I will gather all of their input and populate a row in the database. What should my approach be? Right now I'm writing forms that store the POST data in a SESSION and then populate the database row at the end, but as soon as I introduce conditional logic from page to page, the sessions break and don't get sent. Any help would be greatly appreciated.