问如果我们有多个商店，我们如何分别获得最后插入的id

EN

public function Save_buyer_info($buyer_information)
{
    //$email= $this->session->userdata('email');
    // print_r($buyer_information);
    $this->db->insert('live_sale_buyers',$buyer_information);   
    return $insert_id = $this->db->insert_id();
}

public function submit_order()
{
    //$data=$this->input->post();
    $name = $this->input->post('txt_name');
    $emailBuyer = $this->input->post('txt_email');
    $number = $this->input->post('txt_number');
    $address = $this->input->post('txt_address');
    $username = $this->session->userdata('username');
    $payMode = $this->input->post('payment_mode');

    $email = $this->session->userdata('email'); // get shop id
    $this->db->where('email', $email);
    $activeUser = $this->db->get('live_sale_users');
    $a = $activeUser->row_array();
    $shopId = $a['shop_id'];

    $buyer_information = array(
        "name" => $name,
        "email" => $emailBuyer,
        "mobile" => $number,
        "address" => $address,
        "done_by" => $username,
        "paymentmode" => $payMode,
        'shop_id' => $shopId,
        'shop_keeper_email' => $email
    );

    $buyer_id = $this->Query_Inventory->Save_buyer_info($buyer_information);
}