• John Huebner

• October 7, 2016 at 6:20 am

You are trying do a search and return posts that have a related post that has a specific title. This will not work. It would be like searching for posts that have a related post where the related post has a specific meta value.

The only way that you can do this is to make the information you want to search for part of the post that your searching for it in. This will require that you create another custom field that can hold the title of the related post.

add_filter('acf/update_value/name=relationship_field', 'my_add_titles_to_post_for_search', 10, 3);
function my_add_titles_to_post_for_search($value, $post_id, $field)( {
  // use a new field, it does not need to be an acf field
  // first delete anything it might hold
  delete_post_meta($post_id, '_hidden_relationship_title');
  if (!empty($value)) {
    $posts = $value;
    if (!is_array($posts)) {
      $posts = array($posts);
    }
    foreach ($posts as $post) {
      // add each related post's title
      add_post_meta($post_id, '_hidden_relationship_title', get_the_title($post), false);
    }
  }
  return $value;
}