function notify_admin_on_registration($user_id) { $user_info = get_userdata($user_id); $email = $user_info->user_email; $username = $user_info->user_login; $message = "A new user has registered:\n\nUsername: $username\nEmail: $email"; wp_mail('[email protected]', 'New User Registration', $message); } add_action('user_register', 'notify_admin_on_registration');