function DecodeSession($sess_string)
{
    // save current session data
    //   and flush $_SESSION array
    $old = $_SESSION;
    $_SESSION = array();

    // try to decode passed string
    $ret = session_decode($sess_string);
    if (!$ret) {
        // if passed string is not session data,
        //   retrieve saved (old) session data
        //   and return false
        $_SESSION = array();
        $_SESSION = $old;

        return false;
    }

    // save decoded session data to sess_array
    //   and flush $_SESSION array
    $sess_array = $_SESSION;
    $_SESSION = array();

    // restore old session data
    $_SESSION = $old;

    // return decoded session data
    return $sess_array;
}