BotDetect 3 PHP CAPTCHA is a website security component designed to protect your registration, comment, poll, guestbook, content submission, and other online forms from automated spam submissions. It generates CAPTCHA images with textual code rendered in them that are easily decipherable to humans -- but not to spam bots. In essence, it allows you to focus on your code or content -- instead of on deleting spam. 'Developer Edition' includes FULL SOURCE CODE and ROYALTY FREE distribution rights.
Key features: Time unlimited and fully functional free version; 60 secure & readable Captcha image styles; 10 secure & accessible Captcha sound styles; Localized Captcha generation, using various Unicode character sets and multi-language sound pronunciations; Custom Captcha image size, format, color scheme; Custom Captcha code length, style, character set, timeouts, generated code filtering; Produces XHTML 1.1 Strict and WCAG AAA compliant markup; Not dependent on other software so it does not bring in any additional dependencies; Includes high-quality samples; Free 24x7 support.