Profile: Tom Gonzales

Problem: I would like to use the standard WordPress gallery shortcode to display a gallery that includes images from my custom fields. If no custom field images are defined, I would like to not show a gallery.

Solution: Since the gallery shortcode requires a comma-separated list of image IDs, but custom fields only store individual image URLs, you must use some custom code to translate your stored image URLs into a comma-separated list of IDs:

function prefix_get_img_ids($atts) {
global $post;
 $postid = isset($atts['post_id']) ? $atts['post_id'] : $post->ID;
 $images[] = get_post_meta($postid, 'wpcf-pc-extra-image-1', true);
 $images[] = get_post_meta($postid, 'wpcf-pc-extra-image-2', true);
 // if you want to include more images, copy + paste here with the appropriate image field slug
 
 $ids = array();
 
 global $wpdb;
 
 foreach($images as $img) {
  $query = "SELECT ID FROM {$wpdb->posts} WHERE guid='$img'";
  $id = $wpdb->get_var($query);
  if($id)
    $ids[] = $id;
 }
 
 return implode(",",$ids);
}
add_shortcode("get_image_ids", "prefix_get_img_ids");

Then you can use the gallery shortcode along with your custom shortcode like so:

[gallery ids="[get_image_ids post_id='12345']"]

Replace '12345' with the numeric ID of the post where your custom field images are defined. Then you must register the get_image_ids function as a 3rd-party shortcode argument in Toolset > Settings > Front-end Content.

If you want to hide the gallery when images are not defined, you can use a conditional.

Relevant Documentation: https://toolset.com/documentation/user-guides/shortcodes-within-shortcodes/
https://toolset.com/documentation/user-guides/conditional-html-output-in-views/