newuser_notify_siteadmin( int $user_id )

function newuser_notify_siteadmin( $user_id ) {
	if ( get_site_option( 'registrationnotification' ) != 'yes' )
		return false;

	$email = get_site_option( 'admin_email' );

	if ( is_email($email) == false )
		return false;

	$user = get_userdata( $user_id );

	$options_site_url = esc_url(network_admin_url('settings.php'));
	/* translators: New user notification email. 1: User login, 2: User IP address, 3: Settings screen URL */
	$msg = sprintf(__('New User: %1$s
Remote IP address: %2$s

Disable these notifications: %3$s'), $user->user_login, wp_unslash( $_SERVER['REMOTE_ADDR'] ), $options_site_url);

	/**
	 * Filters the message body of the new user activation email sent
	 * to the network administrator.
	 *
	 * @since WP-MU (3.0.0)
	 *
	 * @param string  $msg  Email body.
	 * @param WP_User $user WP_User instance of the new user.
	 */
	$msg = apply_filters( 'newuser_notify_siteadmin', $msg, $user );
	wp_mail( $email, sprintf(__('New User Registration: %s'), $user->user_login), $msg );
	return true;
}