Guida per creare un box invia email alla propria casella di posta, da utilizzare in uno spazio web che supporti il php

<?php
/*
* This is a PHP library that handles calling reCAPTCHA.
* - Documentation and latest version
* http://recaptcha.net/plugins/php/
* - Get a reCAPTCHA API Key
* http://recaptcha.net/api/getkey
* - Discussion group
* http://groups.google.com/group/recaptcha
*
* Copyright (c) 2007 reCAPTCHA -- http://recaptcha.net
* AUTHORS:
* Mike Crawford
* Ben Maurer
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

/**
* The reCAPTCHA server URL's
*/
define("RECAPTCHA_API_SERVER", "http://api.recaptcha.net");
define("RECAPTCHA_API_SECURE_SERVER", "https://api-secure.recaptcha.net");
define("RECAPTCHA_VERIFY_SERVER", "api-verify.recaptcha.net");

/**
* Encodes the given data into a query string format
* @param $data - array of string elements to be encoded
* @return string - encoded request
*/
function _recaptcha_qsencode ($data) {
$req = "";
foreach ( $data as $key => $value )
$req .= $key . '=' . urlencode( stripslashes($value) ) . '&';

// Cut the last '&'
$req=substr($req,0,strlen($req)-1);
return $req;
}



/**
* Submits an HTTP POST to a reCAPTCHA server
* @param string $host
* @param string $path
* @param array $data
* @param int port
* @return array response
*/
function _recaptcha_http_post($host, $path, $data, $port = 80) {

$req = _recaptcha_qsencode ($data);

$http_request = "POST $path HTTP/1.0\r\n";
$http_request .= "Host: $host\r\n";
$http_request .= "Content-Type: application/x-www-form-urlencoded;\r\n";
$http_request .= "Content-Length: " . strlen($req) . "\r\n";
$http_request .= "User-Agent: reCAPTCHA/PHP\r\n";
$http_request .= "\r\n";
$http_request .= $req;

$response = '';
if( false == ( $fs = @fsockopen($host, $port, $errno, $errstr, 10) ) ) {
die ('Could not open socket');
}

fwrite($fs, $http_request);

while ( !feof($fs) )
$response .= fgets($fs, 1160); // One TCP-IP packet
fclose($fs);
$response = explode("\r\n\r\n", $response, 2);

return $response;
}



/**
* Gets the challenge HTML (javascript and non-javascript version).
* This is called from the browser, and the resulting reCAPTCHA HTML widget
* is embedded within the HTML form it was called from.
* @param string $pubkey A public key for reCAPTCHA
* @param string $error The error given by reCAPTCHA (optional, default is null)
* @param boolean $use_ssl Should the request be made over ssl? (optional, default is false)

* @return string - The HTML to be embedded in the user's form.
*/
function recaptcha_get_html ($pubkey, $error = null, $use_ssl = false)
{
if ($pubkey == null || $pubkey == '') {
die ("To use reCAPTCHA you must get an API key from <a href='http://recaptcha.net/api/getkey'>http://recaptcha.net/api/getkey</a>");
}

if ($use_ssl) {
$server = RECAPTCHA_API_SECURE_SERVER;
} else {
$server = RECAPTCHA_API_SERVER;
}

$errorpart = "";
if ($error) {
$errorpart = "&amp;error=" . $error;
}
return '<script type="text/javascript" src="'. $server . '/challenge?k=' . $pubkey . $errorpart . '"></script>

<noscript>
<iframe src="'. $server . '/noscript?k=' . $pubkey . $errorpart . '" height="300" width="500" frameborder="0"></iframe><br>
<textarea name="recaptcha_challenge_field" rows="3" cols="40"></textarea>
<input type="hidden" name="recaptcha_response_field" value="manual_challenge">
</noscript>';
}




/**
* A ReCaptchaResponse is returned from recaptcha_check_answer()
*/
class ReCaptchaResponse {
var $is_valid;
var $error;
}


/**
* Calls an HTTP POST function to verify if the user's guess was correct
* @param string $privkey
* @param string $remoteip
* @param string $challenge
* @param string $response
* @return ReCaptchaResponse
*/
function recaptcha_check_answer ($privkey, $remoteip, $challenge, $response)
{
if ($privkey == null || $privkey == '') {
die ("To use reCAPTCHA you must get an API key from <a href='http://recaptcha.net/api/getkey'>http://recaptcha.net/api/getkey</a>");
}

if ($remoteip == null || $remoteip == '') {
die ("For security reasons, you must pass the remote ip to reCAPTCHA");
}



//discard spam submissions
if ($challenge == null || strlen($challenge) == 0 || $response == null || strlen($response) == 0) {
$recaptcha_response = new ReCaptchaResponse();
$recaptcha_response->is_valid = false;
$recaptcha_response->error = 'incorrect-captcha-sol';
return $recaptcha_response;
}

$response = _recaptcha_http_post (RECAPTCHA_VERIFY_SERVER, "/verify",
array (
'privatekey' => $privkey,
'remoteip' => $remoteip,
'challenge' => $challenge,
'response' => $response
)
);

$answers = explode ("\n", $response [1]);
$recaptcha_response = new ReCaptchaResponse();

if (trim ($answers [0]) == 'true') {
$recaptcha_response->is_valid = true;
}
else {
$recaptcha_response->is_valid = false;
$recaptcha_response->error = $answers [1];
}
return $recaptcha_response;

}

/**
* gets a URL where the user can sign up for reCAPTCHA. If your application
* has a configuration page where you enter a key, you should provide a link
* using this function.
* @param string $domain The domain where the page is hosted
* @param string $appname The name of your application
*/
function recaptcha_get_signup_url ($domain = null, $appname = null) {
return "http://recaptcha.net/api/getkey?" . _recaptcha_qsencode (array ('domain' => $domain, 'app' => $appname));
}

function _recaptcha_aes_pad($val) {
$block_size = 16;
$numpad = $block_size - (strlen ($val) % $block_size);
return str_pad($val, strlen ($val) + $numpad, chr($numpad));
}

/* Mailhide related code */

function _recaptcha_aes_encrypt($val,$ky) {
if (! function_exists ("mcrypt_encrypt")) {
die ("To use reCAPTCHA Mailhide, you need to have the mcrypt php module installed.");
}
$mode=MCRYPT_MODE_CBC;
$enc=MCRYPT_RIJNDAEL_128;
$val=_recaptcha_aes_pad($val);
return mcrypt_encrypt($enc, $ky, $val, $mode, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0");
}


function _recaptcha_mailhide_urlbase64 ($x) {
return strtr(base64_encode ($x), '+/', '-_');
}

/* gets the reCAPTCHA Mailhide url for a given email, public key and private key */
function recaptcha_mailhide_url($pubkey, $privkey, $email) {
if ($pubkey == '' || $pubkey == null || $privkey == "" || $privkey == null) {
die ("To use reCAPTCHA Mailhide, you have to sign up for a public and private key, " .
"you can do so at <a href='http://mailhide.recaptcha.net/apikey'>http://mailhide.recaptcha.net/apikey</a>");
}


$ky = pack('H*', $privkey);
$cryptmail = _recaptcha_aes_encrypt ($email, $ky);

return "http://mailhide.recaptcha.net/d?k=" . $pubkey . "&c=" . _recaptcha_mailhide_urlbase64 ($cryptmail);
}

/**
* gets the parts of the email to expose to the user.
* eg, given johndoe@example,com return ["john", "example.com"].
* the email is then displayed as john...@example.com
*/
function _recaptcha_mailhide_email_parts ($email) {
$arr = preg_split("/@/", $email );

if (strlen ($arr[0]) <= 4) {
$arr[0] = substr ($arr[0], 0, 1);
} else if (strlen ($arr[0]) <= 6) {
$arr[0] = substr ($arr[0], 0, 3);
} else {
$arr[0] = substr ($arr[0], 0, 4);
}
return $arr;
}

/**
* Gets html to display an email address given a public an private key.
* to get a key, go to:
*
* http://mailhide.recaptcha.net/apikey
*/
function recaptcha_mailhide_html($pubkey, $privkey, $email) {
$emailparts = _recaptcha_mailhide_email_parts ($email);
$url = recaptcha_mailhide_url ($pubkey, $privkey, $email);

return htmlentities($emailparts[0]) . "<a href='" . htmlentities ($url) .
"' onclick=\"window.open('" . htmlentities ($url) . "', '', 'toolbar=0,scrollbars=0,location=0,statusbar=0,menubar=0,resizable=0,width=500,height=300'); return false;\" title=\"Reveal this e-mail address\">...</a>@" . htmlentities ($emailparts [1]);

}


?>