AntiTeori

recaptcha are the anti spam method using captcha. may captcha just using leter and or number but recaptcha using 2 word in different image with AES (Advance Encryption System) on sending the code.
this is available in wordpress plugin called WP-reCAPTCHA

CodeIgniter is a powerful PHP framework with a very small footprint, built for PHP coders who need a simple and elegant toolkit to create full-featured web applications. Blablabla….

This is a CI implementation of the ReCAPTCHA server (http://www.recaptcha.net)

There are three files needed: