How do you refer to the names in the PHP code? How can I make the PHP handle next and previous? Any ideas?

I am currently trying to make a four question quiz. Each question is on a new page. There will be a previous button and a next button to take the user to the previous and next question respectively. There will also be a save button to save the current answer selected for the questions so far. Finally, I will have a submit button that will submit all the answers of the quiz and give back a score. I have to use these buttons, and I have to have my...