Serving pages based on user input

Hi, I am fairly new to PHP. I would like to serve a page to a user based on his input. Say, I have a page 1 where user has 3 options(drop down menu). Based on his selection I would like a php script to direct him to another page (to pages 2,3,4 based on what he selected). I am unable to figure how to do this in php. Can you please give me some pointers. Is there any function which takes path and directs the user to that page? Thanks, Prasad