Author: Gustavo Bordoni

Earlier today I ran into a problem where I needed a simple way to display which registered users are online right now on the site.

I’ve done a Video explaining what was my solution and how to apply it to a theme, but I myself hate when I see a video without any code that I can easily take a look at, so below the video you will find a explanation of the code step by step, and in the end the plugin I created for this purpose.

Please note that I will comment further the code on the video, but there are some comments on each one of the snippets here

—

## Variables used
We will use only two variables on this plugin:

– `static protected $_instance = null;` — Holds the static instance of our class after the plugin is initialized
– `static protected $prefix = ‘OnlineNow’;` — Prefix we will use on the Database Options

## Class Instance handling

When dealing with plugins in WordPress a good practice is to save a static variable of the main class on a private/protected variable and create a static method to instantiate the class whenever you call this method the first time:

“`php
static public function instance(){
null === self::$_instance and self::$_instance = new self;
return self::$_instance;
}
“`

## Plugin Initialization
Here is where our plugin will hook into WordPress and do the required actions to allot this plugin to work as we expect.

“`php
static public function init(){
// Lock this class to be initialized only once
if ( null !== self::$_instance ){
return false;
}
add_action( ‘wp_login’, array( self::instance(), ‘login’ ), 10, 2 );
add_action( ‘clear_auth_cookie’, array( self::instance(), ‘logout’ ), 10 );

// Register Shortcodes
add_shortcode( ‘online:list’, array( self::instance(), ‘shortcode_list’ ) );
add_shortcode( ‘online:qty’, array( self::instance(), ‘shortcode_qty’ ) );

add_filter(‘widget_text’, ‘do_shortcode’);

return true;
}
“`

## Register when a User logs in

We need to register when a user do the login so that we can save it in the database to grab this value and display for the users.

“`php
public function login( $user_login, $user ) {
$users = get_option( self::$prefix . ‘-users’, array() );

if ( in_array( $user->ID, $users ) ){
return;
}

$users[] = $user->ID;

update_option( self::$prefix . ‘-users’, $users );
}
“`

## Register when a User logs out
Just like when we register the action of login and add the user ID to the database option, now we will remove that ID when the user logs out.

“`php
public function logout() {
$users = get_option( self::$prefix . ‘-users’, array() );

$user_id = get_current_user_id();

if ( ! in_array( $user_id, $users ) ){
return;
}

update_option( self::$prefix . ‘-users’, array_diff( $users , array( $user_id ) ) );
}
“`

## Grab the users logged in
We need a method that will allow us to get the users from the database option, I’ve also allowed the developer to exclude or include a user to the list.

“`php
public function get_users( $include = array(), $exclude = array() ){
// Retrieve the users from Database
$users = get_option( self::$prefix . ‘-users’, array() );

// Parse Shortcode atts to exclude
if ( is_string( $exclude ) ){
$exclude = array_map( ‘trim’, explode( ‘,’, $exclude ) );
}

// Exclude users based on shortcode attribute
$users = array_diff( (array) $users, (array) $exclude );

// Parse Shortcode atts to include
if ( is_string( $include ) ){
$include = array_map( ‘trim’, explode( ‘,’, $include ) );
}

// Include users based on shortcode attribute
$users = array_merge( (array) $users, (array) $include );

// Garantee that the array is safe for usage
$users = array_unique( array_filter( (array) $users ) );

// Remove all non existent users
$users = array_map( array( $this, ‘user_exists’ ), $users );

// Garantee that the array is safe for usage
$users = array_filter( (array) $users );

return $users;
}
“`

Then I used a method inside of the `get_users` to check if the user exists before return the list of `WP_User` objects – *[on video](http://www.youtube.com/watch?v=k8W5O0Cpfog&t=19m47s)*.

“`php
public function user_exists( $user_id ){
$user = new WP_User( $user_id );

// Check if the users exists
if ( ! $user->exists() ){
return false;
}

return $user;
}
“`

## List Online Users Shortcode
After we did all the hard work of storing the data about user on the database, now we will use that information to print an HTML with the list of users that are currently online.

“`php
public function shortcode_list( $atts ) {
$atts = (object) shortcode_atts( array(
‘avatar’ => false,

‘exclude’ => ”,
‘include’ => ”,
), $atts );

$users = $this->get_users( $atts->include, $atts->exclude );

$html = ‘

‘;
foreach ( (array) $users as $user ) {
$html .= ‘
• ‘;
  // Allow the user to control the avatar size and if he wants to show
  if ( is_numeric( $atts->avatar ) ){
  $html .= get_avatar( $user , $atts->avatar );
  }
  $html .= ‘‘ . $user->display_name . ‘‘;
  $html .= ‘

‘;
}
$html .= ‘

‘;
return $html;
}
“`

## Display the quantity of Users Online
The user might also want to display the quantity of users that are online with a shortcode, so we will deal with that too.

“`php
public function shortcode_qty( $atts ) {
$atts = (object) shortcode_atts( array(
‘plural’ => __( ‘%s users online’, ‘online-now’ ),
‘singular’ => __( ‘One user online’, ‘online-now’ ),
‘zero’ => __( ‘Zero users online’, ‘online-now’ ),

‘numeric’ => false,

‘exclude’ => ”,
‘include’ => ”,
), $atts );

$users = $this->get_users( $atts->include, $atts->exclude );

if ( $atts->numeric ){
return count( $users );
}

if ( count( $users ) === 0 ) {
$text = $atts->zero;
} elseif ( count( $users ) === 1 ) {
$text = $atts->singular;
} else {
$text = $atts->plural;
}

return sprintf( $text, count( $users ) );
}
“`

## Repository and Download

You can always checkout the oficial repository for this plugin and/or download the latest version of the code to install it in your WordPress.

GitHub Repository
Download Plugin