display.php

<?php
session_start();

if (!isset($_SESSION['keyID']) || !isset($_SESSION['vCode'])) {
    //User tried to go here but didn't submit a keyid/vcode yet
    $_SESSION['error'] = 'Please submit a key ID and verification code';
    header('Location: index.php');
}

//Validate the key ID and vcode again - always ASSUME that there is a possibility they are invalid
$keyID = $_SESSION['keyID'];
$vCode = $_SESSION['vCode'];

if (!$valid_data) {
    $_SESSION['error'] = "Your Key ID and Verification are invalid";
    header('Location: index.php');
}

//do whatever to display relevant data based on $keyID and $vCode
?>