Using PHP and Mysql you can keep track of the users online your website and display it on your page.

First thing ,we need a table in our Mysql database for the users online. So let’s make a table in our database.

mysql_query("CREATE TABLE online(
id INT(11) NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id),
ip_address VARCHAR(25) NOT NULL,
timestamp VARCHAR(25) NOT NULL)") or die(mysql_error());

Now that we have the table, we need to update the users online on every page. That way it is most accurate and up to date with who is currently online. We will set a time offset so that we include all users online within the past 5 minutes.

<?php

// We need to get the user's ip address to check in the database. We'll make a function called ipaddress().
function ipaddress(){
if(getenv('HTTP_CLIENT_IP')) {
$ip = getenv('HTTP_CLIENT_IP');
}
elseif(getenv('HTTP_X_FORWARDED_FOR')) {
$ip = getenv('HTTP_X_FORWARDED_FOR');
}
elseif(getenv('HTTP_X_FORWARDED')) {
$ip = getenv('HTTP_X_FORWARDED');
}
elseif(getenv('HTTP_FORWARDED_FOR')) {
$ip = getenv('HTTP_FORWARDED_FOR');
}
elseif(getenv('HTTP_FORWARDED')) {
$ip = getenv('HTTP_FORWARDED');
}
else {
$ip = $_SERVER['REMOTE_ADDR'];
}
return $ip;
}

$time_offset = time() - (60*5);
$ip = ipaddress();
$sql = mysql_query("SELECT id FROM online WHERE ip_address = '$ip' LIMIT 1") or die(mysql_error());

if(mysql_num_rows($sql) > 0){
mysql_query("UPDATE online SET timestamp = '".time()."' WHERE ip_address = '$ip') or die(mysql_error());
} else {
mysql_query("INSERT INTO online (ip_address,timestamp) VALUES ('$ip','".time()."')") or die(mysql_error());
}
$delete = mysql_query("DELETE FROM online WHERE timestamp < '$time_offset'") or die(mysql_error());

?>

Now every time someone goes on a page with this code, mysql will check to see if the user is in the system, and if so update their current timestamp, otherwise create a row for them in the table. It will also erase any rows with old timestamps. This will keep the table clean and updated.

Now we count the users online and show it on the page.

<?php

function online(){
$time_offset = time() - (60*5);
$sql = mysql_query("SELECT * FROM online WHERE timestamp > '$time_offset'");
$online = mysql_num_rows($sql);

return 'There are '.$online.' user(s) currently online. ';
}
?>

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