Get Data Options In Order

How to obtain detailed data product options in order?
In link:
the choice, the options are in Medium Size
fn_create_order_details function ($ order_id, $ cart)
$order_details = array (
'item_id' => $k,
'order_id' => $order_id,
'size' => $size,
'extra' => serialize($extra)
I want to get value $ size to Medium, then how? Thank you all

help me

Assuming you want this on the cart page before checkout completes. If so, add the following to the page you're interested in and then do a view source to see the structure of the $cart.products.

You can then see the data structures you need to access to get the information you are interested in.