Set a custom field as featured image caption

• sockwell

• December 26, 2019 at 7:55 am

I would like to set the contents of a custom field called featured_image_author as the caption for that post’s featured image. Is that possible?

• John Huebner

• December 28, 2019 at 2:25 am

You need to create an acf/save_post filter and update the image post with it

add_filter('acf/save_post', 'update_featured_image_caption', 20, 1);
function update_featured_image_caption($post_id) {
  // get the featured image id of the post
  $id = get_post_thumbnail_id();
  // if not set, exit
  if (!$id) {
    return;
  }
  // get the field you want to use for the image captions
  $excerpt = get_field('your-field-name', $post_id);
  // if not set, exit
  if (!$excerpt) {
    return;
  }
  // get the attachment post
  $attachment = get_psot($id);
  // alter the caption (post_excerpt)
  $attachment->post_excerpt = $excerpt;
  // disable this filter to prevent infinite loop
  remove_filter('acf/save_post', 'update_featured_image_caption', 20);
  // update the attachment post
  wp_update_post($attachment);
  // re-enable this filter
  add_filter('acf/save_post', 'update_featured_image_caption', 20, 1);
}

• sockwell

• March 16, 2020 at 9:58 am

It caused a critical error when I updated a post.

• John Huebner

• March 17, 2020 at 10:59 pm

Turn on debugging, there might be an error in my code since I typed it here https://codex.wordpress.org/WP_DEBUG

• dandolino100

• August 22, 2022 at 6:18 pm

Support pointed out that there is a typo, but this worked perfectly for me. Fixed typo below:

add_filter('acf/save_post', 'update_featured_image_caption', 20, 1);
function update_featured_image_caption($post_id) {
  // get the featured image id of the post
  $id = get_post_thumbnail_id();
  // if not set, exit
  if (!$id) {
    return;
  }
  // get the field you want to use for the image captions
  $excerpt = get_field('your-field-name', $post_id);
  // if not set, exit
  if (!$excerpt) {
    return;
  }
  // get the attachment post
  $attachment = get_post($id);
  // alter the caption (post_excerpt)
  $attachment->post_excerpt = $excerpt;
  // disable this filter to prevent infinite loop
  remove_filter('acf/save_post', 'update_featured_image_caption', 20);
  // update the attachment post
  wp_update_post($attachment);
  // re-enable this filter
  add_filter('acf/save_post', 'update_featured_image_caption', 20, 1);
}