Use this script in your contact form, for you whois query tool or just there where some extra validation is needed. A session will be created inside a dynamic image file (requires GD library). The random value of this image appears inside the generated image. The user has to enter this value into formfield. This value will be checked while processing the form. Without entering this value a form will not be processed.

By : olaf

<?php /*
example of usage:

inside your form
<input type="text" name="validator" id="validator" size="4" />
<img src="random.php" alt="" width="60" height="20" vspace="1" align="top" />

and test the value of the "validator" form field like:
if (!empty($_POST['validator']) && $_POST['validator'] == $_SESSION['rand_code']) {
process your form here
at least destroy the session
unset($_SESSION['rand_code']);
*/

// save this code in your random script
session_start();

if (empty($_SESSION['rand_code'])) {
$str = "";
$length = 0;
for ($i = 0; $i < 4; $i++) {
// this numbers refer to numbers of the ascii table (small-caps)
$str .= chr(rand(97, 122));
}
$_SESSION['rand_code'] = $str;
}

$imgX = 60;
$imgY = 20;
$image = imagecreatetruecolor(60, 20);

$backgr_col = imagecolorallocate($image, 238,239,239);
$border_col = imagecolorallocate($image, 208,208,208);
$text_col = imagecolorallocate($image, 46,60,31);

imagefilledrectangle($image, 0, 0, 60, 20, $backgr_col);
imagerectangle($image, 0, 0, 59, 19, $border_col);

$font = "VeraSe.ttf"; // it's a Bitstream font check www.gnome.org for more
$font_size = 10;
$angle = 0;
$box = imagettfbbox($font_size, $angle, $font, $_SESSION['rand_code']);
$x = (int)($imgX - $box[4]) / 2;
$y = (int)($imgY - $box[5]) / 2;
imagettftext($image, $font_size, $angle, $x, $y, $text_col, $font, $_SESSION['rand_code']);

header("Content-type: image/png");
imagepng($image);
imagedestroy ($image);
?>

DISCLAIMER: The content provided in this article is not warranted or guaranteed by Developer Shed, Inc. The content provided is intended for entertainment and/or educational purposes in order to introduce to the reader key ideas, concepts, and/or product reviews. As such it is incumbent upon the reader to employ real-world tactics for security and implementation of best practices. We are not liable for any negative consequences that may result from implementing any information covered in our articles or tutorials. If this is a hardware review, it is not recommended to open and/or modify your hardware.

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