How to search users globally on a multisite install?

Question

I'm using the REST API to create/update/delete users on a multisite install in order to sync data with a 3rd party resource. When I am checking whether to update or create a user, I'm using the search parameter to search on usernames, which works fine on a single site, but if a user exists in the system on a different site, how can I tell beyond trying the insert, which triggers a Username is already in use error? I've found this proposed change, which looks to be exactly what I need, but it hasn't made it into code yet. How can I achieve this? I don't mind writing a custom endpoint and doing it in PHP, but I can't find any functions that allows searching globally for users. Even WP_User_Query appears limited to one blog at a time.

Answer 1

It appears you can do this using a blog_id of 0:

$args = array( 'blog_id' => 0 );
$users = get_users( $args );
var_dump( $users );

If you want to search for a specific user, the process is similar:

$args = array( 'blog_id' => 0, 'search' => '{username to search for}' );
$users = get_users( $args );
var_dump( $users );

I discovered this while poking around in the wp-cli source code (since I knew that wp user list --network would return a list of all the users on a Multisite network). It's corroborated by a user comment on the WP_User_Query::prepare_query() documentation.