on another site that i’m helping to develop, i’ve integrated Carnegie Mellon University’s incredible reCaptcha script into PunBB (the forum software running on that site).

reCAPTCHA channels the effort spent solving CAPTCHAs online into correcting OCR mistakes for scanned books.

because the current release of PunBB is not plugin friendly, integrating reCaptcha isn’t a one step process, but with barely any effort it’s completely doable.

PunBB 1.2.15 was used.

Here’s how to do it:

(text version: recaptcha_and_punbb.txt)

INSTALLING reCaptcha into PunBB

1. Download the reCAPTCHA PHP Library and extract recaptchalib.php into your root PunBB directory.

2. Sign up for an API key.

3. Edit your PunBB register.php file:

Find:
define('PUN_ROOT', './');
require PUN_ROOT.'include/common.php';
And add these lines below it:
require_once('recaptchalib.php');
$publickey = "youpublickey";
$privatekey = "yourprivatekey";
Find:
else if (isset($_POST['form_sent']))
{
And add these lines below it:
$resp = recaptcha_check_answer ($privatekey,
$_SERVER["REMOTE_ADDR"],
$_POST["recaptcha_challenge_field"],
$_POST["recaptcha_response_field"]);
Find:
Look for the block of code that begins with:
// Validate username and passwords
if (strlen($username) < 2)
message($lang_prof_reg['Username too short']);
And add these lines below that block of checks:
( below: message($lang_prof_reg[’Username BBCode’]); )
else if (!$resp->is_valid) {
message("The <b>reCAPTCHA</b> wasn't entered correctly. Go back and try it again.");
}
Find:
Near the bottom of the file, find:
<p><input type="submit" name="register" value="<?php echo $lang_register['Register'] ?>" /></p>
And add these lines ABOVE it:
<div class="inform">
<fieldset>
<legend>Are you human?</legend>
<?php echo recaptcha_get_html($publickey, $error); ?>
</fieldset>
</div>
(above the submit button!)

5. That’s it!
NOTE: copying and pasting the code from above might result in ugliness. use the text version: recaptcha_and_punbb.txt to make things easier.