recaptcha problem

[PHPDevil]

hi guys, I have a issue i believe with my recaptcha on my email page.

i downloaded the script and installed it and ran it properly. it shows up but my problem is at the checking part in which it always says it fails.

for the actual checking i have this

 

require_once('recaptchalib.php');
         $privatekey = "FILTERED OUT";
   $resp = recaptcha_check_answer ($privatekey,
                                   $_SERVER["REMOTE_ADDR"],
                                   $_POST["recaptcha_challenge_field"],
                                   $_POST["recaptcha_response_field"]);



if (!$resp->is_valid) {
                 $error_string .= '<center>The reCAPTCHA wasnt entered correctly. Go back and try it again.</center><br />';
       }
   else if ($user == '') {
   $error_string .= '<center>You left the Username field blank!.</center><br />';
   }

 

would be grateful if anyone can see the issue.

I also had this error mes

PHP Fatal error: Call to undefined function recaptcha_check_answer()

that stopped after i changed require_once to require and back again.

not sure whats going on here