使用Doctrine ArrayCollection进行分页？

I have an ArrayCollection I would like to use as the basis of pagination. Typically, I simply use a custom DQL query with thesetFirstResult and setMaxResults methods, but it doesn't make much sense for me to do so since I already have the ArrayCollection of entities in hand (no point in extra DB queries).

My current skeleton is:

public function showOrdersAction($page)
{
    $this->denyAccessUnlessGranted('IS_AUTHENTICATED_FULLY');

    $perPage = 10;
    $user = $this->getUser();
    $orders = $user->getPreviousOrders();

    $maxPages = ceil(count($orders) / $perPage);
}

I'm just unsure how to actually progress from here.