added_existing_user WordPress Action Hook

The added_existing_user hook is called when an existing user is added to a blog. This hook is similar to the user_register hook, but is only called when an existing user is added to a blog. This can happen when a user is added to a blog through the admin interface, or when a user signs up for a new blog through the signup process. This hook can be used to perform any actions that should happen when a new user is added to a blog, such as sending a welcome email or adding the user to a mailing list.

do_action( 'added_existing_user', int $user_id, true|WP_Error $result ) #