How to add captcha to your form

1. Download the recaptcha library here
2. Sign up for a captcha key here
3. Copy recaptchalib.php from your unzipped library to the directory your form will be in
4. Put this into your form :
   

   require_once('recaptchalib.php');
   $publickey = "..."; // you got this from the signup page
   echo recaptcha_get_html($publickey);
   

5. Put this into your processing page:
   

   require_once('recaptchalib.php');
   $privatekey = "...";
   $resp = recaptcha_check_answer ($privatekey,
                                  $_SERVER["REMOTE_ADDR"],
                                  $_POST["recaptcha_challenge_field"],
                                  $_POST["recaptcha_response_field"]);
   
   if (!$resp->is_valid) {
    die ("The reCAPTCHA wasn't entered correctly. Go back and try it again." .
         "(reCAPTCHA said: " . $resp->error . ")");
   }