$_GET , undefined index n

Currently making a Quiz application and I'm almost done. Having ap roblem with my question page though which is reading from my database. In my index.php file I have a link to start the quiz here <a href = "questions.php?n=1" class = "start"> Start Quiz </a> I've also connected to my database in a file called database.php. Here is my questions.php page, and I'm trying to set $number equal to the n=1 portion of the link I set in index.php. I'm sure i've done something exactly like this in the past. Any help? <?php include "database.php"; ?> <?php session_start(); ?> <?php $number = (int) $_GET['n']; $query = "SELECT * FROM questions"; $query.= " WHERE question_number = $number"; $result = mysqli_query($connection,$query); $question = mysqli_fetch_assoc($result); ?>