Insert auto increment using insert_id

[eluser]Ralanyo[/eluser]
I have searched to forums for this and the documentation and can't find an example if anyone can help, i'd appreciate it. Thanks

I just wrote a simple function that inserts into two tables fine but i'm having trouble with the insert_id(). Im trying to get the auto increment primary key of the salesperson table to insert into the salespersonid field of the company table. Here is my code, what am i doing wrong. Sorry for the newbie question

Code:

public function insertMore()
{
    $company = array(
    'companyname' => $this->input->post('company'),
    'salespersonid' => $this->db->insert_id()
       );
      
    $sales = array(
    'name' => $this->input->post('salesrep')
       );
      
       $id = array (
      
       );
    
       $results = array (
       $this->db->insert('company', $company),
       $this->db->insert('salesperson', $sales),
      
       );
      
       return $results;
}