<?php
session_start();

$width  = 120;
$height =  40;
$length =   5;

$baseList = '0123456789abcdfghjkmnpqrstvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

$code    = "";
$counter = 0;

$image = @imagecreate($width, $height) or die('Cannot initialize GD!');

for( $i=0; $i<10; $i++ ) {
   imageline($image,
         mt_rand(0,$width), mt_rand(0,$height),
         mt_rand(0,$width), mt_rand(0,$height),
         imagecolorallocate($image, mt_rand(150,255),
                                    mt_rand(150,255),
                                    mt_rand(150,255)));
}

for( $i=0, $x=0; $i<$length; $i++ ) {
   $actChar = substr($baseList, rand(0, strlen($baseList)-1), 1);
   $x += 10 + mt_rand(0,10);
   imagechar($image, mt_rand(3,5), $x, mt_rand(5,20), $actChar,
      imagecolorallocate($image, mt_rand(0,155), mt_rand(0,155), mt_rand(0,155)));
   $code .= strtolower($actChar);
}

header('Content-Type: image/jpeg');
imagejpeg($image);
imagedestroy($image);

$_SESSION['securityCode'] = $code;

?>