Pass multi-dimensional array to hidden form

[eluser]rochellecanale[/eluser]
Yes i am serializing it but my problem is i only get the last values in my multidimensional array. Here is my sample code.

In my process page

Code:

$product_id = $chunks[0];   //get product id
                 $product_qty = $chunks[1]; //get qty
                 $product_code = $code; //get code
                 $product_name = $name;//get name
                 $product_desc = $desc; //get description
                 $product_price = $price; //get price
                 $product_amount = $product_price*$product_qty; //compute
                
                 //get selected product and assign to array
                 $transact = array(
                    $product_id => array(
                        'product_name' => $product_name,
                        'product_desc' => $product_desc,
                        'product_price' => $product_price,
                        'product_qty' => $product_qty,
                        'product_amount' => $product_amount,
                        'product_code' => $product_code
                    )
                 );
                        //assign array to session
                        foreach($transact as $value){
                            $serialize = serialize($value);
                            $this->session->set_userdata('product_list',$serialize);
                        }

In my result page

Code:

echo "<pre>";
  $unserialize = unserialize($this->session->userdata('product_list'));
  print_r($unserialize);

My other problem is the id in my array it does not viewed. What should i put in the index field?