QuestionCaptcha - The User Friendly Captcha
QuestionCaptcha is simple PHP library that is easy to integrate into your php forms and provies you with Turing test – based captcha protection. It is based on your own defined questions that users need to answer to pass the form.
You can use exact string matches, number ranges and even REGULAR EXPRESSIONS!!!! This may look very simple, but it is a killer feature of my captcha. Check the live demos to see it in action!
One question can have more right answers (useful for example for numbers – 50 and fifty are both corrent answers on question “How much is 60-10?”).