Method getProductDiscountsById

/*
 * ID ... id of product
 */
public static function getProductDiscountsById($id = 0, $returnArray = 0)
{
    if (is_null($id)) {
        throw new Exception('Function Error: No id added', 500);
        return false;
    }
    $id = (int) $id;
    if (!array_key_exists($id, self::$product)) {
        $db = Factory::getDBO();
        $user = PhocacartUser::getUser();
        $userLevels = implode(',', $user->getAuthorisedViewLevels());
        $userGroups = implode(',', PhocacartGroup::getGroupsById($user->id, 1, 1));
        $wheres = array();
        $wheres[] = "a.product_id = " . (int) $id;
        $wheres[] = "a.access IN (" . $userLevels . ")";
        $wheres[] = " (ga.group_id IN (" . $userGroups . ") OR ga.group_id IS NULL)";
        $where = count($wheres) ? ' WHERE ' . implode(' AND ', $wheres) : '';
        $query = 'SELECT a.id, a.title, a.alias, a.discount, a.access, a.calculation_type, a.quantity_from, a.valid_from, a.valid_to' . ' FROM #__phocacart_product_discounts AS a' . ' LEFT JOIN #__phocacart_item_groups AS ga ON a.id = ga.item_id AND ga.type = 4' . $where . ' ORDER BY a.id';
        $db->setQuery($query);
        if ($returnArray) {
            $discounts = $db->loadAssocList();
        } else {
            $discounts = $db->loadObjectList();
        }
        self::$product[$id] = $discounts;
    }
    return self::$product[$id];
}