php: clase para recaptcha

No sé si habéis tenido que trabajar alguna vez con recaptcha de php, pero me resulta muy cutre tener funciones por ahí sueltas sin encapsular en una clase:

recaptcha.class.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
*          https://www.google.com/recaptcha/admin/create
*    - 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.
*/

class recaptcha
{
  const RECAPTCHA_API_SERVER = 'http://www.google.com/recaptcha/api';
  const RECAPTCHA_API_SECURE_SERVER = 'https://www.google.com/recaptcha/api';

  const RECAPTCHA_VERIFY_SERVER = 'www.google.com';

  public $publickey;
  public $privatekey;

  private $error;

  /**
  * Encodes the given data into a query string format
  * @param $data - array of string elements to be encoded
  * @return string - encoded request
  */
  private function _recaptcha_qsencode($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 $data
  * @param int port
  * @return array response
  */
  private function _recaptcha_http_post($host, $path, $data, $port = 80)
  {
    $req = $this -> _recaptcha_qsencode($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.
  */
  public function get_html($use_ssl = false)
  {
    $pubkey = $this -> publickey;

    if ($pubkey == null || $pubkey == '')
      die("To use reCAPTCHA you must get an API key from <a href='https://www.google.com/recaptcha/admin/create'>https://www.google.com/recaptcha/admin/create</a>");

    if ($use_ssl)
      $server = self::RECAPTCHA_API_SECURE_SERVER;
    else
      $server = self::RECAPTCHA_API_SERVER;

    $errorpart = "";
    if ($this -> error)
      $errorpart = "&amp;error=" . $this -> 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>';
  }

  /**
  * 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
  * @param array $extra_params an array of extra variables to post to the server
  * @return ReCaptchaResponse
  */
  public function check_answer($remoteip, $challenge, $response, $extra_params = array())
  {
    $this -> resetError();
    $privkey = $this -> privatekey;

    if ($privkey == null || $privkey == '')
      die("To use reCAPTCHA you must get an API key from <a href='https://www.google.com/recaptcha/admin/create'>https://www.google.com/recaptcha/admin/create</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)
    {
      $this -> error = 'incorrect-captcha-sol';
      return false;
    }

    $response = $this -> _recaptcha_http_post(self::RECAPTCHA_VERIFY_SERVER, "/recaptcha/api/verify", array('privatekey' => $privkey, 'remoteip' => $remoteip, 'challenge' => $challenge, 'response' => $response) + $extra_params);

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

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

  /**
  * 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 $appname The name of your application
  */
  private function recaptcha_get_signup_url($domain = null, $appname = null)
  {
    return "https://www.google.com/recaptcha/admin/create?" . $this -> _recaptcha_qsencode(array('domains' => $domain, 'app' => $appname));
  }

  private 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 */

  private 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 = $this -> _recaptcha_aes_pad($val);
    return mcrypt_encrypt($enc, $ky, $val, $mode, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0");
  }

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

  /* gets the reCAPTCHA Mailhide url for a given email, public key and private key */
  public function mailhide_url($email)
  {
    $pubkey = $this -> publickey;
    $privkey = $this -> privatekey;

    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://www.google.com/recaptcha/mailhide/apikey'>http://www.google.com/recaptcha/mailhide/apikey</a>");

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

    return "http://www.google.com/recaptcha/mailhide/d?k=" . $pubkey . "&c=" . $this -> _recaptcha_mailhide_urlbase64($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
  */
  private 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://www.google.com/recaptcha/mailhide/apikey
  */
  public function mailhide_html($email)
  {
    $pubkey = $this -> publickey;
    $privkey = $this -> privatekey;

    $emailparts = $this -> _recaptcha_mailhide_email_parts($email);
    $url = $this -> mailhide_url($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]);
  }

  private function resetError()
  {
    $this -> error = NULL;
  }

  public function getError()
  {
    if ($this -> error)
      return $this -> error;
    return false;
  }
}
?>

para probarlo:
recaptcha.example.php

<?php
require_once('recaptcha.class.php');

$captcha = new recaptcha();
$captcha->privatekey = 'PRIVATEKEY';
$captcha->publickey = 'PUBLICKEY';

if ($_POST["recaptcha_response_field"])
{
  $resp = $captcha->check_answer
  (
    $_SERVER["REMOTE_ADDR"],
    $_POST["recaptcha_challenge_field"],
    $_POST["recaptcha_response_field"]
  );

  if ($resp)
    echo "You got it!";
  else
    echo $captcha->getError();
}
?>
<html>
<body>
<form action="" method="post">
<br/>
<?php
echo $captcha->get_html();
?>
<input type="submit" value="submit" />
</form>
</body>
</html>

 

mailhide:
recaptcha.mailhide.php

<?php
require_once ("recaptcha.class.php");
$captcha = new recaptcha();
$captcha->privatekey = 'PRIVATEKEY';
$captcha->publickey = 'PUBLICKEY';
?>
<html><body>
The Mailhide version of example@example.com is
<? echo $captcha->mailhide_html("example@example.com"); ?>. <br>

The url for the email is:
<? echo $captcha->mailhide_url ("example@example.com"); ?> <br>

</body></html>
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