create a new file leave it blank, but save it as usersonline.txt

now make a new file, and add the following script:

<?
$remote = $_SERVER["REMOTE_ADDR"];
$file = "usersonline.txt";
$timeoutseconds = 60; //how long the user stays on, before classed offline which can be changed
$timestamp = time();
$timeout = ($timestamp-$timeoutseconds);
$fp = fopen("$file", "a+");
$write = $remote."||".$timestamp."\n";
fwrite($fp, $write);
fclose($fp);
$online_array = array();
$file_array = file($file);
foreach($file_array as $newdata){
list($ip, $time) = explode("||", $newdata);
if($time >= $timeout){
array_push($online_array, $ip);
}
}
$online_array = array_unique($online_array);
$online = count($online_array);
if($online == "1"){
echo "Users Online: $online";
}else{
echo "Users Online: $online";
}
?>

save this as usersonline.php

now, once you have uploaded both files, and chmoded usersonline.txt to 777. You should include the following script where you would like the number of users online to show up:

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

Example for this page:

Warning: fopen(usersonline.txt) [function.fopen]: failed to open stream: Permission denied in /home/stealth/public_html/php/usersonline.php on line 7

Warning: fwrite(): supplied argument is not a valid stream resource in /home/stealth/public_html/php/usersonline.php on line 9

Warning: fclose(): supplied argument is not a valid stream resource in /home/stealth/public_html/php/usersonline.php on line 10
Users Online: 0