Pimcore\Model\Listing\AbstractListing::setOrder PHP Method

    public function setOrder($order)
    {
        $this->order = [];
        if (is_string($order) && !empty($order)) {
            $order = strtoupper($order);
            if (in_array($order, $this->validOrders)) {
                $this->order[] = $order;
            }
        } elseif (is_array($order) && !empty($order)) {
            $this->order = [];
            foreach ($order as $o) {
                $o = strtoupper($o);
                if (in_array($o, $this->validOrders)) {
                    $this->order[] = $o;
                }
            }
        }
        return $this;
    }