id   |   product_name   |   price   |   qty   |   subtotal

//array code from unserialized function
    $products = unserialize($this->session->userdata('product_list'));

//This is the output.
Array
(
    [2] => Array
        (
            [id] => 2
            [product_name] => NOKIA 5110
            [product_desc] => Cellphone
            [product_price] => 500.00
            [product_qty] => 1
            [product_amount] => 500
            [product_code] => NOKI2012-84353
        )

    [3] => Array
        (
            [id] => 3
            [product_name] => HP IPAQ RW6828
            [product_desc] => Cellphone
            [product_price] => 1500.00
            [product_qty] => 1
            [product_amount] => 1500
            [product_code] => HP I2012-08386
        )
)

function  __construct()
    {

        parent::__construct();
        $this->load->model('model_name','',TRUE);
    }
function add()
{
//products stuff
$acknowledgement = $this->model_name->add_data($products);
}

function add_data($data)
{
 foreach($data as $blah)
 {
   $bar = array(
    'product_name' => $blah['product_name'],
    'price' => $blah['product_price'],
    'qty' => $blah['product_qty'],
    'subtotal' => 5,
   );
 $this->db->insert('sales_table',$bar)
 }
}

foreach($products as $p) {
    $data = array(
        'product_name' => $p['product_name'],
        'price' => $p['product_price'],
        'qty' => $p['product_qty'],
        'subtotal' => 1, // what do you want here?
    );

    $data2 = array(
        'product_stuff' => $p['product_code'],
        'product_stuffo' => 100 * $p['product_amount'], // anything you want
    );


    $this->db->insert('products', $data);
    $this->db->insert('sales_line', $data2);
}