if(isset($_POST['update'])){
	foreach($_POST['book'] as $book_id => $amount){
		$amount = intval($amount);
		if($amount <= 0){
			$cart->remove($book_id);
			// echo "REMOVING BOOK";
		} else {
			$cart->update($book_id,"amount",$amount);
			// echo "UPDATING BOOK WITH AMOUNT: ".$amount;
		}
	}
	$cart->save();
}