Sort invoices by product name

[tkowalczyk]

Hello

I`m trying to sort invoices by product name, I noticed that I need to write some static function in Order class, because in pdf.php file is code like this:

$invoices = Order::getOrdersIdInvoiceByDate($_GET['date_from'], $_GET['date_to'], NULL, 'invoice');
   if (is_array($invoices))
       PDF::multipleInvoices($invoices);

so could somebody help me to write correct sql query that will be in this function
thanks in advance
tomek