wp-includes/ms-functions.php:2293Adds a user to a blog based on details from maybe_add_existing_user_to_blog().
$detailsarray|falseoptionalfalse$user_idint
$rolestring
true|WP_Error|nullOne hook fires while add_existing_user_to_blog() runs, in this order:
Fires immediately after an existing user is added to a site.
function add_existing_user_to_blog( $details = false ) { if ( is_array( $details ) ) { $blog_id = get_current_blog_id(); $result = add_user_to_blog( $blog_id, $details['user_id'], $details['role'] ); /** * Fires immediately after an existing user is added to a site. * * @since MU (3.0.0) * * @param int $user_id User ID. * @param true|WP_Error $result True on success or a WP_Error object if the user doesn't exist * or could not be added. */ do_action( 'added_existing_user', $details['user_id'], $result ); return $result; } return null;}Introduced in MU (3.0.0). One change between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
true|WP_Error|void to true|WP_Error|null.verified against sourcesrc/wp-includes/ms-functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.