1add_filter('posts_clauses', 'order_by_stock_status');
2function order_by_stock_status($posts_clauses) {
3 global $wpdb;
4 // only change query on WooCommerce loops
5 if (is_woocommerce() && (is_shop() || is_product_category() || is_product_tag() || is_product_taxonomy())) {
6 $posts_clauses['join'] .= " INNER JOIN $wpdb->postmeta istockstatus ON ($wpdb->posts.ID = istockstatus.post_id) ";
7 $posts_clauses['orderby'] = " istockstatus.meta_value ASC, " . $posts_clauses['orderby'];
8 $posts_clauses['where'] = " AND istockstatus.meta_key = '_stock_status' AND istockstatus.meta_value <> '' " . $posts_clauses['where'];
9 }
10 return $posts_clauses;
11}
12