Try this modified human_code.php:
PHP Code:
<?php
function randchr() {
$chr_array = array(chr(rand(48,57)), chr(rand(65,90)), chr(rand(97,122)) );
return $chr_array[rand(0,2)];
}
session_start();
// generate random characters and output it as an image
$code = randchr().randchr().randchr().randchr().randchr();
$im = @imagecreate(60, 20) or die("Cannot Initialize new GD image stream");
$background_color = imagecolorallocate($im, 255, 255, 255);
$text_color = imagecolorallocate($im, 233, 14, 91);
imagestring($im, 4, 3, 3, $code, $text_color);
$_SESSION['code'] = $code;
header("Content-type: image/gif");
imagegif($im);
imagedestroy($im);
?>
Hope it helps..