Easy to implement captcha with codeigniter?

I'm using CodeIgniter开发者_StackOverflow中文版 and need an easy to implement captcha. Something simple, nothing too complicated. Any ideas?

https://github.com/EllisLab/CodeIgniter/wiki/ReCAPTCHA <-- would recaptcha work for you?

Try using ReCaptcha - http://recaptcha.net/ - it's easy and has PHP API too.

A list of 12 essential captchas. Captchator for example looks easy to implement.

If you wish to use captcha because of spam messages I would advice you to also look at akismet or typepad antispam

Making your own captcha script could also be fun. With php gd library it is not too hard to accomplish. Ofcourse, there is no point in reinventing the wheel and using scripts like recaptcha is much safer, but like I said - it could be fun.

The best solution was provided by nettuts.com, but for the codeigniter, the best solution is right here. http://codeigniter.com/wiki/captcha/

In order to integrate to your script, you have to analyze the API.