Joomla Custom PayPal IPN

/**
 * Description of IPNConfig
 *
 * @author Alex
 */
class IPNConfig {
    
    public static $PAYPAL_EMAIL = "accoutn@gmail.com";
    public static $SECURE_MERCHANT_ACCOUNT_ID = "123456789"; 
        
    public static $ADDRESS = "ssl://www.sandbox.paypal.com";
    public static $PORT = 443;
    public static $TIMEOUT  = 30;    
}

/*
 * @version     $Id$
 * @author      Oleksandr Balyuk <obalyuk@boolcast.com>
 * @license     http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL v2
 * Creation Date:   26 June, 2009
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * ------------------------------------------------------------------------
 *
 * MUST BE LOCATED INSIDE OF SOME COMPONENT DERECTORY
 * ON THE SITE SIDE (NOT ADMINISTRATOR/COMPOENTS)
 * FOR EXAMPLE: /components/com_ipn/
 *
 * IF YOU CANT TO PLACE IT INTO DIFFERENT DIRECTORY MAKE SURE
 * $path = split(DS."component", $path);
 * IS EVALUATED TO ROOT OF SITE
 *
 */

//  Prevent Direct User Access (Need Transaction Type)
if (!isset($_POST["txn_type"]))
    die;

// Set flag that this is a parent file
define('_JEXEC', 1);
define('DS', DIRECTORY_SEPARATOR);

$path = dirname(__FILE__);
$path = split(DS . "component", $path);

define('JPATH_BASE', $path[0]);
define('JPATH_COMPONENT', JPATH_BASE . DS . 'components' . DS . 'com_ipn');

require_once ( JPATH_BASE . DS . 'includes' . DS . 'defines.php' );
require_once ( JPATH_BASE . DS . 'includes' . DS . 'framework.php' );
require_once (JPATH_COMPONENT . DS . 'IPNConfig.php');
$mainframe = & JFactory::getApplication('site');
$mainframe->initialise();


//  Log the Transaction into the IPN Transaction Log [PTIONAL]
// @todo add loggin logic
//  Prevent User Access (Continue only if Transaction ID is set)
if (!isset($_POST["txn_id"]))
    die;


// Read the post from PayPal system and add 'cmd'
$req = 'cmd=_notify-validate';
foreach ($_POST as $key => $value) {
    $value = urlencode(stripslashes($value));
    $req .= "&$key=$value";
}


// Post back to PayPal to validate
$server = IPNConfig::$ADDRESS;
$port = IPNConfig::$PORT;
$timeout = IPNConfig::$TIMEOUT;

$header .= "POST /cgi-bin/webscr HTTP/1.0\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Content-Length: " . strlen($req) . "\r\n\r\n";

$fp = fsockopen($server, $port, $errno, $errstr, $timeout);


// Process validation from PayPal
if (!$fp) {
    // HTTP ERROR
} else {

    // NO HTTP ERROR
    fputs($fp, $header . $req);

    while (!feof($fp)) {
        $res = fgets($fp, 1024);
        if (strcmp($res, IPNConfig::$VERIFIED) == 0) {

            //  Validate IPN
            if (IPNMAnager::getInstance()->isValid($_POST)) {
                //  Process Payment
                // @todo add processing logic

                break;  //  Exit the loop
            }
        } else if (strcmp($res, IPNConfig::$INVALID) == 0) {
            //  Log the INVALID IPN Transaction for manual invenstigation
            // @todo add loggin invalid logic
            break;  //  Exit the loop
        }
    }
    fclose($fp);
}
?>