Users_model::username_check PHP Method

    public function username_check($username, $id = '')
    {
        $this->db->select('user_username')->from('users')->where('user_username', $username);
        if (is_numeric($id)) {
            $this->db->where('user_id !=', $id);
        }
        $query = $this->db->get();
        if ($query->num_rows() > 0) {
            return FALSE;
        }
        return TRUE;
    }