Visitors Online - With PHP (no MySQL is needed)

<?
$timeout = 15; // change it. It is the timer which will delete the member of  online list (in minutes)
if (!$datei) $datei = dirname(__FILE__)."/online.txt";
$time = @time();
$ip = $REMOTE_ADDR;
$string = "$ip|$time\n";
$a = fopen("online.txt", "a+");
fputs($a, $string);
fclose($a);
$timeout = time()-(60*$timeout);
$all = "";
$i = 0;
$datei = file("online.txt");
for ($num = 0; $num < count($datei); $num++) {
$pieces = explode("|",$datei[$num]);

 if ($pieces[1] > $timeout) {
  $all .= $pieces[0];
  $all .= ",";
 }
$i++;
}

$all = substr($all,0,strlen($all)-1);
$arraypieces = explode(",",$all);
$useronline = count(array_flip(array_flip($arraypieces)));

echo $useronline;

$dell = "";
for ($numm = 0; $numm < count($datei); $numm++) {
$tiles = explode("|",$datei[$numm]);
 if ($tiles[1] > $timeout) {
  $dell .= "$tiles[0]|$tiles[1]";
 }
}
if (!$datei) $datei = dirname(__FILE__)."/online.txt";
$time = @time();
$ip = $REMOTE_ADDR;
$string = "$dell";
$a = fopen("online.txt", "w+");
fputs($a, $string);
fclose($a);
?>