wp-includes/ms-functions.php:162Adds a user to a blog, along with specifying the user's role.
$blog_idint$user_idint$rolestringtrue|WP_Error2 hooks fire while add_user_to_blog() runs, in this order:
Filters whether a user should be added to a site.
Fires immediately after a user is added to a site.
function add_user_to_blog( $blog_id, $user_id, $role ) { switch_to_blog( $blog_id ); $user = get_userdata( $user_id ); if ( ! $user ) { restore_current_blog(); return new WP_Error( 'user_does_not_exist', __( 'The requested user does not exist.' ) ); } /** * Filters whether a user should be added to a site. * * @since 4.9.0 * * @param true|WP_Error $retval True if the user should be added to the site, error * object otherwise. * @param int $user_id User ID. * @param string $role User role. * @param int $blog_id Site ID. */ $can_add_user = apply_filters( 'can_add_user_to_blog', true, $user_id, $role, $blog_id ); if ( true !== $can_add_user ) { restore_current_blog(); if ( is_wp_error( $can_add_user ) ) { return $can_add_user; } return new WP_Error( 'user_cannot_be_added', __( 'User cannot be added to this site.' ) ); } if ( ! get_user_meta( $user_id, 'primary_blog', true ) ) { update_user_meta( $user_id, 'primary_blog', $blog_id ); $site = get_site( $blog_id ); update_user_meta( $user_id, 'source_domain', $site->domain ); } $user->set_role( $role ); /** * Fires immediately after a user is added to a site. * * @since MU (3.0.0) * * @param int $user_id User ID. * @param string $role User role. * @param int $blog_id Blog ID. */ do_action( 'add_user_to_blog', $user_id, $role, $blog_id ); clean_user_cache( $user_id ); wp_cache_delete( $blog_id . '_user_count', 'blog-details' ); restore_current_blog(); return true;}Introduced in MU (3.0.0). Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/ms-functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.