Online PHP editor | output for fHJN5

<?php $_GET['guess'] = 61; $a = $_GET['guess']; $b = 60; $c = "Missing Guess Parameter"; $d = "Your guess is too low"; $e = "Your guess is not a number"; $f = "Your guess is too high"; $g = "Congratulations - You are right"; if (!isset($a)) { echo $c; } elseif ($a < $b) { echo $d; } elseif (!is_numeric($a)) { echo $e; } elseif ($a > $b) { echo $f; } else { echo $g; }