Security Image for forms with php?

[karlosio]

How do I make a security image that displays random letters and numbers so the user can input them into a form before submitting like what they have on forum registrations? :confused:

[oracle128]

http://www.white-hat-web-design.co.uk/articles/php-captcha.php
http://www.ejeliot.com/pages/2
http://www.puremango.co.uk/cm_php_captcha_script_113.php

[karlosio]

Nice one, thanks oracle :)