PHP-Captcha-CSRF
Easy Captcha and CSRF generation. Will give protection for your form input.
See the example.php for details.
The CSRF Protection
Check is for the code.
Also is a time limit of 5 minutes.
And a check for REMOTE_ADDR, the submitting IP.
The CAPTCHA
Has many settings to modify the captcha image.
See the inc/captcha_img.php.