[WordPress] Adding Custom Information to a WordPress Category Edit Page

00-acme-display-object-ids.php

<?php

add_action('edit_category_form', 'acme_display_object_ids');
/**
 * Displays an ordered list of all of the object IDs for a given
 * taxonomy.
 */
function acme_display_object_ids()
{
  // Code for displaying the Object IDs goes here.
}

01-object-id-subscriber.php

<?php

class ObjectIdSubscriber
{
    /**
     * @var string the hook to which this class subscribes
     */
    private $hook;
  
    /**
     * @param string $hook the hook to which this class is registered with WordPress
     */
    public function __construct(string $hook)
    {
      $this->hook = $hook;
    }

    /**
     * Renders all of the information for the object IDs.
     */
    public function load()
    {
        // Code for displaying the Object IDs goes here.
    }
}

02-term-taxonomy-id.php

<?php

// This will retrieve all of the term relationships from where we can get post IDs.
global $wpdb;
$termTaxonomyId = $wpdb->get_results(
    $wpdb->prepare(
        "
        SELECT DISTINCT term_taxonomy_id
        FROM $wpdb->term_taxonomy
        WHERE term_id = %s
        ",
        $tagId
    ),
    ARRAY_A
);
$termTaxonomyId = isset($termTaxonomyId[0]) ? $termTaxonomyId[0] : null;
if (null === $termTaxonomyId) {
    return null;
}

03-object-ids.php

<?php

// This will retrieve all of the post IDs.
$postIds = $wpdb->get_results(
    $wpdb->prepare(
        "
        SELECT object_id
        FROM $wpdb->term_relationships
        WHERE term_taxonomy_id = %s
        ",
        $termTaxonomyId
    ),
    ARRAY_A
);
if (empty($postIds)) {
    return null;
}

04-render-data.php

<ul>
<?php foreach ($postIds as $postId) : ?>
  <li><?php echo $postId; ?></li>
<?php endforeach; ?>
</ul>