WordPress dashboard widget to show logged in users

functions.php

/**
 * Creates the new widget section to the administration dashboard if the user has the administrator user role.
 *
 * https://www.nuno-sarmento.com
 */
add_action('wp_dashboard_setup', 'm1ka_online_users_widget');
function m1ka_online_users_widget() {
	if ( current_user_can( 'manage_options' ) ) {
		wp_add_dashboard_widget( 'm1ka_online_users', 'Users Stats', 'm1ka_online_users' );
	}
}

/**
 * Runs on each page load.
 * If the user does not exist in the array in the 'online_status' transient, then add them.
 */
function  user_online_update(){

	if ( is_user_logged_in() ) {

		// get the user activity the list
		$logged_in_users = get_transient( 'online_status' );

		// get current user ID
		$user = wp_get_current_user();

		// check if the current user needs to update his online status;
		// he does if he doesn't exist in the list
		// and if his "last activity" was less than let's say: 1 minutes ago
		$no_need_to_update = isset( $logged_in_users[$user->ID] ) && $logged_in_users[$user->ID] >  ( time() - ( 1 * 60 ) );

		// update the list if needed
		if ( ! $no_need_to_update ) {
			$logged_in_users[$user->ID] = time();
			set_transient( 'online_status', $logged_in_users, $expire_in = (  1 * 60 ) ); // 2 mins
		}
	}
}
add_action( 'wp', 'user_online_update' );

/**
 * Runs when a user logs out.
 * If the user exists in the 'online_status' array, remove them from there and update the transient.
 */
function clear_transient_on_logout() {

	$user_id = get_current_user_id();

	$users_transient_id = get_transient( 'online_status' );

	if ( is_array( $users_transient_id ) ) {
		if ( $users_transient_id[$user_id] ) {
			unset( $users_transient_id[$user_id] );
			set_transient( 'online_status', $users_transient_id, ( 1 * 60 ) ); // 2 mins
		}
	}
}
add_action( 'clear_auth_cookie', 'clear_transient_on_logout' );

/**
 * The contents of the widget
 */
// Adds the content to the widget section
function m1ka_online_users() {

	$logged_in_users = count(get_transient('online_status')); // gets number of logged-in users
	$total_users = count_users(); // gets user info

   	echo '<div style="width: 48%; float: left; text-align: center;"><h1>';
   	_e('Total Users: ', 'm1ka_ouw');
   	echo $total_users['total_users'];
   	echo '</h1></div>';

   	echo '<div style="width: 48%; float: left; text-align: center;"><h1>';
   			_e('Online Users: ', 'm1ka_ouw');
   				echo $logged_in_users;
   	echo '</h1></div><div style="clear: both;"></div>';
}