this id?

[eluser]smdelektronik[/eluser]
$this->db->trans_start();

$this->db->select_max('user_id');
$query = $this->db->get('users');
$id = $query->row()->user_id+1;

$data = array(
'username' => $username . $id ,
'password' => $password,
);

$this->db->insert('users', $data);
...
$this->db->trans_complete();


my solution is this, but maybe some1 have better solution.
hope you understand now