DevPapers - article How Many Users Online?

You can easily show how many users are online with PHP and MySQL! Follow this quick tutorial:

The MySQL Part

First of all you will need to create a table in your MySQL Database:

CREATE TABLE `useronline` (
`timestamp` int(15) NOT NULL default '0',
`ip` varchar(40) NOT NULL default '',
`file` varchar(100) NOT NULL default '',
PRIMARY KEY (`timestamp`),
KEY `ip` (`ip`),
KEY `file` (`file`)
) TYPE=MyISAM;

Showing The Users

You now need to create a file called useronline.php. Fill out the configuration with your own information:

<?
// -------------------------------------
// Configuration
// -------------------------------------

$dbhost = "localhost";
$dbuser = ""; // MySQL Username
$dbpass = ""; // MySQL Password
$dbname = ""; // Database Name
$timeoutseconds = 300; // How long till it will remove the user from the database(In seconds)

// -------------------------------------

$timestamp=time();
$timeout=$timestamp-$timeoutseconds;
// Connect to MySQL Database
mysql_connect($d_host,$dbuser,$dbpass);
@mysql_select_db($dbname) or die("Unable to select database");
// Add this user to database
mysql_query("insert into useronline values('$timestamp','$REMOTE_ADDR','$PHP_SELF')") or die("MySQL Error: ".mysql_error());
// Dlete users that have been online for more then "$timeoutseconds" seconds
mysql_query("delete from useronline where timestamp<$timeout") or die("MySQL Error: ".mysql_error());
// Select users online
$result = mysql_query("select distinct ip from useronline") or die("MySQL Error: ".mysql_error());
$user = mysql_num_rows($result);
// Select users on this very page
$resulta = mysql_query("select distinct ip from useronline where file='$PHP_SELF'") or die("MySQL Error: ".mysql_error());
$usera = mysql_num_rows($resulta);
mysql_close();

// Show all users online
if ($user==1) {echo"$user user online!";} else {echo"$user users online.";}
// Show users on this very page
if ($usera==1) {echo" $user user viewing this page!";} else {echo"$user users viewing this page.";}
?>

Now you need to include it on everypage:

<?php
include("useronline.php");
?>

That's everything! Enjoy!