In some previous posts, I have talked about getting WordPress Multisite to work across separate domains instead of using subdomains as it was intended. It works with some manual wrangling, but the sites didn’t appear in the Super Admin section that multisite adds to the back end. I decided to try and fix that problem.

The main issue here comes from the table wp_blogs. In that table there are blog ids and site ids. This points to the intent to allow separate domains and separate subdomains in the same install. The problem is that functionality is intended more for a hosted site solution and the separate sites are protected from one another. To make separate domains works, the blogs need to have different site_ids. This is the crux of the problem as the admin takes the current site_id into account when making the blog list in the super admin. To fix the problem, I removed the reference to site_id from the queries.

in wp-admin/ms-sites.php there are several queries that populate the multisite admin and some code to protect sites from one another. Since my files are edited, I cannot give accurate line numbers, so please bare with me. Searching for site_id, you will find the following lines:

if ( $details->site_id != $wpdb->siteid )
  wp_die( __( 'You do not have permission to access this page.' ) );

These lines get commented out. Next, you should find:

$query = "SELECT * FROM {$wpdb->blogs} WHERE site_id = '{$wpdb->siteid}' ";

I replace this with:

$query = "SELECT * FROM {$wpdb->blogs}";

Then comes:

$query = "SELECT *
FROM {$wpdb->blogs}, {$wpdb->registration_log}
WHERE site_id = '{$wpdb->siteid}'
AND {$wpdb->blogs}.blog_id = {$wpdb->registration_log}.blog_id
AND {$wpdb->registration_log}.IP LIKE ('%{$like_s}%')";

replaced by:

$query = "SELECT *
FROM {$wpdb->blogs}, {$wpdb->registration_log}
WHERE {$wpdb->blogs}.blog_id = {$wpdb->registration_log}.blog_id
AND {$wpdb->registration_log}.IP LIKE ('%{$like_s}%')";

After making these edits, all my sites appeared on the super admin list and so far I have not found any other issues. Use these changes at your own risk. This has not been heavily tested. As time goes on, if I find more issues, I will pass on the information. These modifications will be used on some rather large sites once all my conversion is done, so the testing will happen. I will keep you informed.