reCAPTCHA example

<html>
<body> <!-- the body tag is required or the CAPTCHA may not show on some browsers -->
your HTML content


<?php
    $publickey = "XXX";
    $privatekey = "YYY";
    require_once('recaptchalib.php');

    if (isset($_POST["recaptcha_response_field"])){
        echo "<pre>";
        print_r($_POST);
        require_once('recaptchalib.php');
        $resp = recaptcha_check_answer ($privatekey,
                                        $_SERVER["REMOTE_ADDR"],
                                        $_POST["recaptcha_challenge_field"],
                                        $_POST["recaptcha_response_field"]);
        print_r($resp);
        print_r($_SERVER);
    }
?>

<form method="post" action="recaptcha.php">
<?php echo recaptcha_get_html($publickey); ?>
<input type="submit" />
</form>

more of your HTML content
</body>
</html>

<!-- Example output for valid entry

Array
(
    [recaptcha_challenge_field] => 03AHJ_VuvHgC572BKLlgNYGK3_6XxQHRI4gakBrWRC9wgenmWDDMWJngNMt-33gV0N9g0AD6qMPnYst38yQ_X2WQkz13ffHLrrU7fmjmvuH42M00T6VH3lZ4QM5VoZb7k5zQChr_vgeuUo9GerHwASwP2mp5hE8ZBI7Q
    [recaptcha_response_field] => iitingn 26
)
ReCaptchaResponse Object
(
    [is_valid] => 1
    [error] =>
)
Array
(
    [UNIQUE_ID] => T5lcRn8AAAEAABCSU-QAAAAH
    [HTTP_HOST] => localhost
    [HTTP_USER_AGENT] => Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20100101 Firefox/11.0
    [HTTP_ACCEPT] => text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
    [HTTP_ACCEPT_LANGUAGE] => en-gb,en-us;q=0.8,en;q=0.5,fr;q=0.3
    [HTTP_ACCEPT_ENCODING] => gzip, deflate
    [HTTP_DNT] => 1
    [HTTP_CONNECTION] => keep-alive
    [HTTP_REFERER] => http://localhost/recaptcha.php
    [CONTENT_TYPE] => application/x-www-form-urlencoded
    [CONTENT_LENGTH] => 226
    [PATH] => /sbin:/usr/sbin:/bin:/usr/bin
    [SERVER_SIGNATURE] =>
Apache/2.2.17 (PCLinuxOS 2011/PREFORK-1pclos2011) Server at localhost Port 80


    [SERVER_SOFTWARE] => Apache/2.2.17 (PCLinuxOS 2011/PREFORK-1pclos2011)
    [SERVER_NAME] => localhost
    [SERVER_ADDR] => 127.0.0.1
    [SERVER_PORT] => 80
    [REMOTE_ADDR] => 127.0.0.1
    [DOCUMENT_ROOT] => /var/www/html
    [SERVER_ADMIN] => root@localhost
    [SCRIPT_FILENAME] => /var/www/html/recaptcha.php
    [REMOTE_PORT] => 50032
    [GATEWAY_INTERFACE] => CGI/1.1
    [SERVER_PROTOCOL] => HTTP/1.1
    [REQUEST_METHOD] => POST
    [QUERY_STRING] =>
    [REQUEST_URI] => /recaptcha.php
    [SCRIPT_NAME] => /recaptcha.php
    [PHP_SELF] => /recaptcha.php
    [REQUEST_TIME] => 1335450694
)
-->