public static function getPostIdByWishlistItemId($id) {
        global $wpdb;

        $table = Master::getWishlistTableName();
        $serial = $wpdb->get_var($wpdb->prepare("SELECT item_serial FROM {$table} WHERE id = %d", $id));
        if ($serial === null) {
            return null;
        }

        $data = unserialize($serial);
        if (empty($data)) {
            return null;
        }

        $ids = array_keys((array)$data);
        $post_id = isset($ids[0]) ? (int)$ids[0] : null;
        if (empty($post_id)) {
            return null;
        }

        return $post_id;
    }