I came up with this handy little PHP script that will pop up a message if the correct code is inputed. I don't see a point to it, but I'm sure someone can use it!
<form name="code" action="<?php echo $_SERVER['PHP_SELF']; ?>" method="get">
<p>For the purposes of this page, the code is 31413. Try entering this and other numbers.</p>
<p>Please enter your coupon code: <input type="text" name="couponcode" /></p>
<p><?php
$code = $_GET['couponcode'];
if ($code == '31413')
{
echo "<font color="green">Congratulations, you have the code!</font></p>";
}
else {
echo "<font color="red">Sorry, the code you entered is incorrect. Please try again.</font></p>";
?>
<input type="submit">
</form>