Hello, if you are developing a web application, you may need this online users script to show how many users is online.
 
Yesterday i wrote a php class for it and decide to share it.
Creating table
 
Well, Before using this class, you must create a table in your database:
 
    CREATE TABLE `online_users` (
 
    `session_id` CHAR(150) NOT NULL,
 
    `last_activity` INT(11) NOT NULL DEFAULT '0'
 
    );
 
Creating php file
 
Next step is create and using 'SA_USERSONLINE' Class!
 
SA_USERSONLINE class:
 
    <?php
 
    /*
     * Author : Reza Ramezanpour <[email protected]>
     * Website: http://softafzar.net
     */
 
    class SA_USERSONLINE
    {
 
    protected $DB_HOST = DB_HOST;
 
    protected $DB_NAME = DB_NAME;
 
    protected $DB_USER = DB_USER;
 
    protected $DB_PWD = DB_PWD;
 
    protected $session_id = null;
 
    protected $time = null;
 
    protected $timeout = 15;
 
    protected $link = null;
 
    protected $stmt = null;
 
    function __construct ()
    {
    session_start();
    $this->session_id = session_id();
    $this->time = time();
    $this->link = mysqli_connect($this->DB_HOST, $this->DB_USER,
    $this->DB_PWD, $this->DB_NAME);
    }
 
    /**
      * Gets current online users
      */
    function get_online_users ()
    {
    $this->delete_update_onlineusers();
    $this->insert_onlineusers();
    $this->stmt = mysqli_query($this->link,
    'SELECT session_id FROM online_users');
    return mysqli_num_rows($this->stmt);
    }
 
    private function already_registred ()
    {
    $this->stmt = mysqli_query($this->link,
    "SELECT session_id FROM online_users WHERE session_id='$this->session_id'");
    if (! $this->stmt || mysqli_num_rows($this->stmt) <= 0)
    return false;
    return true;
    }
 
    private function insert_onlineusers ()
    {
    if (! $this->already_registred()) {
    mysqli_query($this->link,
    "INSERT INTO online_users VALUES('$this->session_id',$this->time)");
    }
    }
 
    private function delete_update_onlineusers ()
    {
    $timeout = $this->time - ($this->timeout * 60);
    mysqli_query($this->link,
    "DELETE FROM online_users WHERE last_activity<=$timeout");
    mysqli_query($this->link,
    "UPDATE online_users SET last_activity=$this->time WHERE session_id='$this->session_id'");
    }
 
    /**
      * Set timeout in minutes.
      *
      * @param int $timeout
      */
    function set_timeout ($timeout)
    {
    $this->timeout = ((int) $timeout);
    }
    }
 
    ?>
 
Example usage:
 
    $usersOnline = new SA_USERSONLINE();
    echo 'Online users: ', $usersOnline->get_online_users();
 
Also, You can customize session timeout(in minutes):
$usersOnline->set_timeout(15);
 
NOTE: If database connection is already established, You should remove lines 34 and 35:
 
    $this->link = mysqli_connect($this->DB_HOST, $this->DB_USER,
    $this->DB_PWD, $this->DB_NAME);