function checkUserLogon ( $username, $password ) {
        $statement = $this->mysqli->stmt_init();
        if ( $statement->prepare(
'SELECT id, username, date_created FROM users WHERE username=? AND password=? ' ) ) {
            $statement->bind_param("ss", $username, $password);
            $statement->execute();

            if ( $statement->affected_rows == 1 ) {
                $statement->bind_result($this->user_id, $this->user_name, $this->user_date_created);
                $statement->fetch();
                return TRUE;
            }
        } else {
            return FALSE;
        }
    }