this is not rfi the f_cms = INC_DIR so u cant include it because it have a value and u cant include this value $f_cms = INC_DIR . 'cmses/' . $GLOBALS['fc_config']['CMSsystem'] . '.php'; if( !file_exists($f_cms) || !is_file($f_cms) ) require_once(INC_DIR . 'cmses/statelessCMS.php');//free for all users else require_once( $f_cms ); so f_cms = INC_DIR --->CAN'T INCLUDE :D