public function getSortableMetaKeys()
    {
        if (!isset($_POST['posttype']) || empty($_POST['posttype'])) {
            echo '0';
            die();
        }

        $meta = \Modularity\Helper\Post::getPosttypeMetaKeys($_POST['posttype']);

        $response = array(
            'meta_keys' => $meta,
            'sort_curr' => get_field('posts_sort_by', $_POST['post']),
            'filter_curr' => get_field('posts_meta_key', $_POST['post']),
        );

        echo json_encode($response);
        die();
    }