Demo: Philip's Guestbook

Please enter this number in the box.

Purpose: This script is a captcha script. Its purpose is to defeat spammer's bots that attempt to write several unsolicited advertising postings in guestbooks, forums...

Requirements: You will need PHP installed and have the GD extension enabled.

Copy and save the following code as form.php in a folder on your webserver.

[Download] (right click -> Save Target As)

<?php $random = rand(100, 9999); ?> <form action="verify.php" method="post"> <INPUT type=hidden value="<?php echo $random;?>" name=random> <FONT face="Trebuchet MS" color=#0000ff> Please enter this number in the box.</font><BR> <img src="captcha.php?<?php echo $random;?>"><BR> <INPUT size=10 name=captcha></P> <P><INPUT type=submit value=" Submit "></P></FORM>

Copy and save the following code as captcha.php in the same folder on your webserver.

[Download] (right click -> Save Target As)

<?php error_reporting(E_ALL ^ E_NOTICE); Header("Content-type: image/png"); //Tells the page this is an image. This must be put before any output. $w = "100"; //Image Width $h = "25"; //IMage Height $QS = $_SERVER['QUERY_STRING']; $number = ((4 * $QS)-18); if (is_numeric($QS)) {$message = $number;} else {$message = "Invalid input!"; $error = 1;} $im = ImageCreate($w, $h); //Start the image. $background_color = imagecolorallocate($im, 220, 220, 220); //Background color. RGB Values. //$BorderColor = imagecolorallocate($im, 0, 10, 20); $text = ImageColorAllocate($im, 97, 97, 95); //Text Color RGB Values ImageRectangle($im,0,0,$w - 1,$h - 1,$BorderColor); // Create the background if (!($error == 1)){ ImageFtText ($im, 14, 0, 10, 18, $text, "courbd.ttf", "$message", array());} elseif ($error == 1){ ImageFtText ($im, 9, 0, 2, 15, $text, "courbd.ttf", "$message", array());} //Write the foreground Text // 8=Font Size 0=Angle 1=Dist from top 10=Dist from left ImagePng($im); //Draws the image ImageDestroy($im); //Finish the image. ?>

Copy and save the following code as verify.php in the same folder on your webserver.

[Download] (right click -> Save Target As)

<?php $verification = false; $equiv = (($_POST['captcha'] + 18 )/ 4) - $_POST['random']; if ($equiv == 0) {$verification = true;} else {echo "There was an error with your submission. Please retry.";} if ($verification == true){ // Verification passed - now what do you want to do? echo "Congratulations, you entered the correct number!"; } ?>

Obviously, this script only generates an image for the captcha and verifies it. You will want to integrate this feature into already-existing scripts to obtain its functionality. Enjoy!

Note: This script calls for the captcha image with a random number placed in the query string. This number is then calculated mathematically to generate the number used for the captcha (hence its usefulness). The number in the query string is not the number shown in the image.
This script has already been successfully used to defeat hundreds of bot submissions!

Note: You use this script at your own risk!

Bugs, comments, questions? Contact Me