In Mambo you can enable CAPTCHA on forms via Administration -> Global Configuration. CAPTCHA is a function that transforms a series of letters and/or digits into an image. The user is asked to type these letters/numbers into a form field. This is a method of spam protection against bots.

In order to use the optional CAPTCHA your server must be configured with the following:

1. a GD or GD2 library, to manipulate images;
2. imagettftext, to transform text into images.

If CAPTCHA isn't working, first check that GD or GD2 is enabled on your server. You can check this via Administration -> System Info -> PHPInfo.

If you are on a local host, or have acces to the php.ini file, change this line:

;extension=php_gd2.dll

to

extension=php_gd2.dll

(delete the semi-colon which disables this function)

To check if the imagettftext function is present access CAPTCHA directly using your browser like so:

http://yourdomain.com/includes/captcha.php

The following error indicates that imagettftext() cannot be found:

Fatal error: Call to undefined function: imagettftext() in /home/hosting/thewiseman/includes/captcha.php on line 96

If you have access to your local server, this might help: http://us2.php.net/imagettftext

If your site is in a shared hosting environment or you use managed hosting services, please contact your host and ask the host to enable these two functions.