This question has been answered by sottwell. See the first response.
define("MGR_DIR", "manager");$base_path = str_replace('\\','/',dirname(__FILE__)) . '/';
if(is_file($base_path . 'assets/cache/siteManager.php'))
include_once($base_path . 'assets/cache/siteManager.php');
if(!defined('MGR_DIR') && is_dir("{$base_path}manager"))
define('MGR_DIR','manager');