/**
  * checks that the session varialbe is set and correct
  * @return void
  */
 function checkAuthorisation($sessionVar)
 {
     if (isset($_SESSION[$sessionVar])) {
         $session_id = stopdirectaccess::makeSessionId();
         $error = $_SESSION[$sessionVar] != $session_id;
     } else {
         $error = true;
     }
     if ($error) {
         exit("You cant access this page directly");
     }
 }
<?php

/*
$Id: attributemanagerplaceholder.inc.php,v 1.1.1.1 2006/12/22 13:37:21 gswkaiser Exp $

osCommerce, Open Source E-Commerce Solutions
http://www.oscommerce.com

Released under the GNU General Public License

Web Development
http://www.kangaroopartners.com
*/
require_once 'attributemanager/includes/attributemanagerconfig.inc.php';
require_once 'attributemanager/classes/stopdirectaccess.class.php';
stopdirectaccess::authorise(AM_SESSION_VALID_INCLUDE);
?>
<div id="attributemanager"></div>
// config
require_once $attributemanager_includes_attributemanager . 'config.inc.php';
// misc functions
require_once $attributemanager_includes_attributemanager . 'functions.inc.php';
// parent class
require_once $attributemanager_classes_dir_attributemanager . $class_php;
// db wrapper
require_once $attributemanager_classes_dir . 'db' . $class_php;
// instant class
require_once $attributemanager_classes_dir_attributemanager . 'instant' . $class_php;
// atomic class
require_once $attributemanager_classes_dir_attributemanager . 'atomic' . $class_php;
// security class
require_once $attributemanager_classes_dir . 'stopdirectaccess' . $class_php;
// check that the file is allowed to be accessed
stopdirectaccess::checkAuthorisation(AM_SESSION_VALID_INCLUDE);
// construct the attributemanager classess and/or session variable
if (!is_numeric($_GET['products_id']) || AM_ATOMIC_PRODUCT_UPDATES) {
    // first time visiting the page - delete the session var and start again
    if ('new_product' == $_GET['pageAction'] && !isset($_GET['amAction'])) {
        if (olc_session_is_registered(AM_SESSION_VAR_NAME)) {
            olc_session_unregister(AM_SESSION_VAR_NAME);
            unset(${AM_SESSION_VAR_NAME});
        }
    }
    // register the session if its not registered
    if (!olc_session_is_registered(AM_SESSION_VAR_NAME)) {
        // declare the var (not nessessary)
        ${AM_SESSION_VAR_NAME} = array();
        // start a new session
        olc_session_register(AM_SESSION_VAR_NAME);