Reply To: featured image from relationship field (backend)

• John Huebner

• November 26, 2023 at 10:33 am

You need to do this with an acf/save_post action.

add_action('acf/save_post', 'copy_image_from_relationship', 20);
function copy_image_from_relationship($post_id) {
  // check the post type
  if (get_post_type($post_id) != 'print-size') {
    // not the right post type
    return;
  }
  // get the post id for the related post
  $related_id = get_field('relationship_field_name', $post_id, false);
  if ($related_id) {
    // get the featured image ID from the related post
    $image_id = get_post_thumbnail_id($related_id);
    if ($image_id) {
      // set on current post being updated
      update_post_meta($post_id, '_thumbnail_id', $image_id);
    }
  }
}