PHPClasses.org is spotlighting another package from their site today - this time it's a CAPTCHA class that takes things a step further and introduces animation into the mix to make it even harder for bots to get through.
Laszlo Zsidi is a PHP Web developer that has written an harder to break CAPTCHA solution. It consists in generating animated GIF images that exhibit the validation text.
Since the text never appears all at once in each of the animated frames, this solution certainly raises the bar in terms of difficulty for the robots to guess the validation text, making it very hard to defeat, if possible at all.
You can check out the class here, including a sample animated gif file and a download of everything you'll need to get started.