In this new article from Edward Eliot on SitePoint today, he walks you through the addition of an image to your form (CAPTCHA-style) to enhance its reliability.

If you're looking for a way to prevent brute-force attacks against your login pages, automated sign-ups through your registration forms, or automated spam in your blog commenting system, then look no further! In this article, I'll guide you through the basics of creating and integrating a security image like those found on the sign-up pages of many mainstream sites.

This tutorial isn't for those new to PHP and dives right into the class code for the SecurityImage. He shows you how to create the image, add some noise, add the characters, and combine them all together. All of the code you'll need is laid out for you - well, that and access to a server running the GD libraries...