Prevent variable update after page refresh without javascript
<p>A friend of mine is developing a web application that's more of an online learning facility. On each page is a set of questions. He wants that when the use has answered all the questions on a page and submitted (and taken to the next page for the next set of questions), he shouldn't be able to go back to answer and resubmit those questions again. The idea is that "opportunity comes but once".  </p>

<p>He doesn't want to use javascript because it can be disabled which leaves him with server-side coding. He uses PHP.  </p>

<p>Is there a solution?</p>
