我还没有对此进行过广泛的测试，但它在发布和更新方面都起到了作用。发布或更新帖子时，它会检查是否设置了父项，获取父项以获取所有父项分类法，然后循环并按分类法将子项分类法设置为父项分类法。

/** Set Child Terms to Parent Terms **/
function set_parent_terms( $post_id, $post ) {
    if ( \'publish\' === $post->post_status && $post->post_parent > 0 ) {
        $parent = get_post($post->post_parent);

        if(!empty($parent)){
            $taxonomies = get_object_taxonomies( $parent->post_type );
            foreach ( (array) $taxonomies as $taxonomy ) {
                $terms = wp_get_post_terms( $parent->ID, $taxonomy );
                if ( !empty( $terms ) ) {
                    $termArr = array_map(create_function(\'$obj\', \'return $obj->term_id;\'), $terms);
                    $tmp = wp_set_object_terms( $post_id, $termArr, $taxonomy, true );
                }
            }
        }
    }
}
add_action( \'save_post\', \'set_parent_terms\', 100, 2 );