/**
  * If this order is still a cart, we save a copy of the items and
  * the subtotal in the session for the quick cart dropdown to be
  * usable even on static cached pages.
  *
  * @param OrderItem $item
  * @param Buyable   $buyable
  * @param int       $quantity
  */
 protected function updateSessionCart($item, $buyable, $quantity)
 {
     if (!session_id() || !$buyable) {
         return;
     }
     $cart = !empty($_SESSION['Cart']) ? $_SESSION['Cart'] : array('Items' => array(), 'SubTotal' => 0.0);
     if ($quantity > 0) {
         if (!isset($cart['Items'][$buyable->ID])) {
             $prod = $item->Product();
             $img = $prod ? $prod->Image() : null;
             $img = $img ? $img->getThumbnail() : null;
             // TODO: the key here should probably include the classname (or cover the diff bt Products and Variations)
             $cart['Items'][$buyable->ID] = array('ThumbURL' => $img ? $img->RelativeLink() : '', 'Link' => $prod ? $prod->RelativeLink() : '', 'Title' => $item->TableTitle(), 'SubTitle' => $item->hasMethod('SubTitle') ? $item->SubTitle() : '', 'UnitPrice' => $item->obj('UnitPrice')->Nice(), 'Quantity' => $quantity, 'RemoveLink' => $item->removeallLink());
         } else {
             // update the quantity if it's already present
             $cart['Items'][$buyable->ID]['Quantity'] = $quantity;
         }
     } else {
         // remove the item if quantity is 0
         unset($cart['Items'][$buyable->ID]);
     }
     // recalculate the subtotal
     $cart['SubTotal'] = $this->owner->obj('SubTotal')->Nice();
     // and the total number of items
     $cart['TotalItems'] = 0;
     foreach ($cart['Items'] as $item) {
         $cart['TotalItems'] += $item['Quantity'];
     }
     $_SESSION['Cart'] = $cart;
 }