Slug / Link to Change
function philosophy_cpt_slug_fix($post_link, $id) { $p = get_post($id); if(is_object($p) && 'chapter' == get_post_type($id)) { $parent_post_id = get_field('parent_book'); $parent_post = get_post($parent_post_id); if($parent_post){ $post_link = str_replace('%book%',$parent_post->post_name, $post_link); } } return $post_link; } add_filter( 'post_type_link', 'philosophy_cpt_slug_fix', 1, 2);