[Typo3-shop] Digital goods / pass value (pagenumber) from list view page to order

[Jens Liesegang]

> The $basket->itemArray will always be available until to the order
> finalization. So you store your data here.
> 
> extend the sendNotifyEmail function and the getBasket function.
> 
> Extend only the $this->itemArray['pid']['itemnumber'] part, because
> otherwise the loops will not work anymore. Here you can add an array of
> pids for a product.

Franz, I have tried my very best but can't figure it out. To add a
document-ID to $this->itemArray['pid']['itemnumber'] I'd like to post this
with 

<input type="hidden" name="ttp_basket[7][documentid]" value="3553" />
<input type="hidden" name="ttp_basket[7][documenttitle]" value="Schweizer
Gesellschaften" />

On a product in single view. But how can I add / access / append this to
$this->itemArray['pid']['itemnumber'] in lines 974ff. ?

Jens