Validating user input with php

The task we had for this exercise was to create a website that first takes user input then validates the given user input and after submitting then redirects to a page that then serves as a confirmation page. All of this was to be done with PHP and by using sessions. The latter part of the exercise was to store user info in cookies and use that info on another page. I'd also like to point out that while all code works and is valid, as required by the assignment, I wrote this post from memory and not while doing the exercise.