Handing the ID from the database to the URL - CodeIgniter - php

Question

I am starting my game with CodeIgniter and I have a problem - I would like to download the ID - of the product from the database so that it will be passed to the URL address:
Example address:
http://localhost/crm-SEO/api/admin/domains/{{ID in database}}/notes
When I have other methods like:
domains/GET/6
domains/update/6
Everything works fine for me, but I can not grasp it that I have domains/{{ID}}/
My code i models:
public function get( $id = false)
{
if ( $id == false ) {
$q = $this->db->get('domains');
$q = $q->result();
}
else{
$this->db->where('id', $id);
$q = $this->db->get('domains');
$q = $q->row();
}
return $q;
}
public function update($domain)
{
$this->db->where('id', $domain['id'] );
$this->db->update('domains', $domain);
}
public function create($domain)
{
$this->db->insert('domains', $domain);
}
public function delete($domain)
{
$this->db->where('id', $domain['id'] );
$this->db->delete('domains');
}
My code in controller:
public function __construct()
{
parent::__construct();
$post = file_get_contents('php://input');
$_POST = json_decode($post,true);
$this->load->model('admin/domains_model');
}
public function get($id = false)
{
$result = $this->domains_model->get($id);
echo '{"records":' . json_encode( $result ) . '}';
}
public function update()
{
$domain = $this->input->post('domain');
$this->domains_model->update($domain);
}
public function create()
{
$domain = $this->input->post('domain');
$this->domains_model->create($domain);
}
public function delete()
{
$domain = $this->input->post('domain');
$this->domains_model->delete($domain);
}