Need a good captcha generating php script

Hello,

I need a good captcha generating php script. I searched on Google but din't found anything useful so far, I am interested in your personal suggestions, some php script that is easy to install and generates strong captchas.

Take a look here. There are a few CAPTCHA scripts there for you to use.

mine is not so "strong" but very easy to use:
http://www.finalwebsites.com/snippets.php?id=39

Thank you for your suggestions! So far I also found Captcha Creator </snipped> which seems easy to install and works nice! ;)

EDIT don't post links commercial websites here...

If you need a php captcha installed on your page, visit my site and click the credits link.. on the credits page theres a link to the best captcha that can easily be integrated on any php project...