private function getOrderAndSeed($order)
    {
        @list($order, $seed) = explode(':', $order, 2);

        if (empty($seed)) {
            $seed = $this->getRandomSeed();
        }

        if (!is_numeric($seed)) {
            $this->showError("Could not use '$seed' as seed.");
        }

        return array($order, $seed);
    }