New PHP CAPTCHA Issue...

[tpsilver10]

So I'm trying to integrate a CAPTCHA field into my current form. I've got this going, but it only ever comes back with 'Wrong Code' - the code is never right...

 

This is input part.

<form action="process.php" method="post" />
/* The Form */
<img src="verificationimage.php?<?php echo rand(0,9999);?>" alt="verification image, type it in the box" width="50" height="24" align="absbottom" />
<br /><br />
Security Code: <input name="verif_box" type="text" id="verif_box" class="formstyles" />
<br /><br />
<input type='submit' value='Submit Form' class="formstyles"> <input type=reset value='Clear Form' class="formstyles">

 

This is the processing bit.

<?php

$verif_box = $_REQUEST["verif_box"];

// check to see if verificaton code was correct
if(md5($verif_box).'a4xn' == $_COOKIE['tntcon']){
process_form();
setcookie('tntcon','');
} else {
echo "Wrong Code";
exit;
}
//Rest of the form
?>

 

The verification image:

<?php
header('Content-type: image/jpeg');

$width = 50;
$height = 24;

$my_image = imagecreatetruecolor($width, $height);

imagefill($my_image, 0, 0, 0xFFFFFF);

// add noise
for ($c = 0; $c < 40; $c++){
$x = rand(0,$width-1);
$y = rand(0,$height-1);
imagesetpixel($my_image, $x, $y, 0x000000);
}

$x = rand(1,10);
$y = rand(1,10);

$rand_string = rand(1000,9999);
imagestring($my_image, 5, $x, $y, $rand_string, 0x000000);

setcookie('tntcon',(md5($rand_string).'a4xn'));

imagejpeg($my_image);
imagedestroy($my_image);
?>