public function insert_user($name, $desc)
{
$this->db->trans_start(TRUE);
$this->db->set('Name', $name);
$this->db->set('Desc', $desc);
$this->db->insert('user');
$id = $this->db->insert_id();
$this->db->trans_complete();
return $id;

if ($this->db->trans_status() === TRUE)
    {
        insert_access($get);
    }

public function insert_access($get)
    {
        $data = $this->input->post('pTableData');
        $tableData = json_decode($data,TRUE);
        foreach ($tableData as $get)
        {
            $this->db->set('UserID', $id);
            $this->db->set('AccessName', $get['accessName']);
            $this->db->set('Password', $get['password']);
            $this->db->insert('access');
            $id_access = $this->db->insert_id();

            return $id_access ;
        }
    }

$id = $this->db->insert_id();
if ($this->db->trans_status() === TRUE)
{
    $this->insert_access($id);                //if in the same model
    $this->another_model->insert_access($id); //if some other model
}