Vistitors Online Script

<?php
$userip = $_SERVER['REMOTE_ADDR'];
$time = time();
$usersonline = 0;
$alreadyonline = 0;
$onlinetxt = fopen("./online.txt","r+");
flock($onlinetxt,2);
while (!feof($onlinetxt)) { 
$user[] = chop(fgets($onlinetxt,65536));
}
fseek($onlinetxt,0,SEEK_SET);
ftruncate($onlinetxt,0);
foreach ($user as $line) {
@list($savedip,$savedtime) = split("|",$line);
if ($savedip == $userip) {
  $savedtime = $time;
  $alreadyonline = 1;
}
if ($time < $savedtime + ($session_length)) {
  fputs($onlinetxt,"$savedip|$savedtime\n");
  $usersonline = $usersonline + 1;
}
}
if (!$alreadyonline) {
fputs($onlinetxt,"$userip|$time\n");
$usersonline = $usersonline + 1;
}
fclose ($onlinetxt);
if($usersonline==1){
echo "<center> 1 user online </center>";
} else {
echo "<center> "$usersonline." users online</center>";
}
?>

echo "<center> "$usersonline." users online</center>";

<!--#include virtual="/server_path_to/onlinecount.cgi" -->