CAPTCHAv2 a question/answer based SPAM protector

What is CAPTCHAv2 and what does question/answer based mean?
I doubt that I am the only one who gets angry at the latest generation of image based CAPTCHAs. They are designed to make it hard for SPAM bots to read the image but they have now made it almost impossible for humans to decipher them as well.
Here is an example of a CAPTCHA generated by Google.com

Or here is another generated by the Simple Machines forum (contains 5 letters)


So I started to design CAPTCHv2, a PHP class written to protect any website form SPAM bots attempting to abuse your website by submitting their garbage to your forms. So instead of presenting you a obfuscated/impossible to read image, my protection will ask the user questions.
The question:
Please remove the letters X and Y from the following word: cXaYXpiXXtalYisXm

Questions can also be tailored to your audience by asking questions only people with knowledge about a specific subject can answer. But be careful not to make the questions too hard or you might deny newcomers access to your resource.

The downside is that the website operator needs to invest a little bit of time creating questions first but this should be a small price to pay for happy customers and to make things easy, you get a management interface.



Describing CAPTCHAv2 in detail will take a bit so I split the information over multiple pages.

• What is CAPTCHAv2 (this page)


• How does CAPTCHAv2 work?


• What are the requirements of CAPTCHAv2?


• CAPTCHAv2 download page


• General installation instructions


• How can CAPTCHAv2 be used to protect a comment form


• How can CAPTCHAv2 be used as a bot trap

• FluxBB 1.2 or 1.4 CAPTCHAv2 implementation guide


• Simple Machines Forum - CAPTCHAv2 implementation guide