Now that I've got the GD module installed and working, it's time to give it something useful to do. In this post I'll describe how to generate and verify a CAPTCHA. Sadly, for the rest of us, spammers have taken to abusing free services available on the web via HTML forms. CAPTCHA is an attempt to limit form users to the human variety, in this case by asking the them to type in the letters displayed in an image.
