Enabling sessions
It is quite possible, that you'll use session variables in the configuration file (config.php), for example when setting up the Access Control or writing the CheckAuthentication() function.
Please remember that you have to start your session before use of $_SESSION becomes available. In most cases it can be done by uncommenting the "session_start()" call in the configuration file:
session_start();
Once enabled, session variables cab be accessed using the global $_SESSION array:
$_SESSION['CKFinder_UserRole'] = "admin";
More information about session handling can be found in PHP manual.