How Parent Taxonomy automatically added to the post when using `wp_set_object_terms()`?
You can use get_ancestors() to get parents and grandparents etc. of a term, then use that in wp_set_object_terms(): $term_id = 12; // Get array of term parents. $terms = get_ancestors( $term_id, ‘topic’ ); // Include original term in array. $terms[] = $term_id; // Add parents and original term to post. wp_set_object_terms( $post_id, $terms, ‘topic’, true … Read more