Your suggestion for grouping items dropdown box  by stock_id instead of by item_code would mean that the user must remember the stock_id for each item_code wanted which may not be feasible. The replacement of the i.description with s.description will render both descriptions the same and would make for ambiguity in selection.

    $sql = "SELECT i.item_code, i.description, c.description, count(*)>1 as kit,
             i.inactive, if(count(*)>1, '0', s.editable) as editable
            FROM
            ".TB_PREF."stock_master s,
            ".TB_PREF."item_codes i
            LEFT JOIN
            ".TB_PREF."stock_category c
            ON i.category_id=c.category_id
            WHERE i.stock_id=s.stock_id";

   
    if ($type == 'local')    { // exclude foreign codes
        $sql .=    " AND !i.is_foreign";
    } elseif ($type == 'kits') { // sales kits
        $sql .=    " AND !i.is_foreign AND i.item_code!=i.stock_id";
    }
    $sql .= " AND !i.inactive AND !s.inactive AND !s.no_sale";
    $sql .= " GROUP BY i.item_code";

to

    $sql = "SELECT i.item_code, s.description, c.description, count(*)>1 as kit,
             i.inactive, if(count(*)>1, '0', s.editable) as editable
            FROM
            ".TB_PREF."stock_master s,
            ".TB_PREF."item_codes i
            LEFT JOIN
            ".TB_PREF."stock_category c
            ON i.category_id=c.category_id
            WHERE i.stock_id=s.stock_id";

   
    if ($type == 'local')    { // exclude foreign codes
        $sql .=    " AND !i.is_foreign";
    } elseif ($type == 'kits') { // sales kits
        $sql .=    " AND !i.is_foreign AND i.item_code!=i.stock_id";
    }
    $sql .= " AND !i.inactive AND !s.inactive AND !s.no_sale";
    $sql .= " GROUP BY i.stock_id";

I enter two foreign extra codes for a product. If i do so and then going to Sales Order Entry in Item Description I am get each product two time. If I enter foreign code one time it shows one time only.

So do we need new table to enter Manufacturer Code and UPC for product.

regards