public static function get_instance() { if (is_null(self::$instance)) { self::$instance = new self(); } return self::$instance; }
function YITH_Product_Slider_Type() { if (!defined('YWCPS_PREMIUM')) { return YITH_Product_Slider_Type::get_instance(); } else { return YITH_Product_Slider_Type_Premium::get_instance(); } }