Someone

<?php
extract($_SERVER);
$cookie_ip = $_COOKIE['client_ip'];
$file = "counter.txt";
$line = file($file);

if(!$cookie_ip) {
  setcookie("client_ip", $REMOTE_ADDR, time()+360000);
  $line[0]++;
  $open = fopen($file, "w+");
  fputs($open, "$line[0]");
  fclose($open);
}

elseif($cookie_ip != $REMOTE_ADDR){
  $line[0]++;
  $open = fopen($file, "w+");
  fputs($open, "$line[0]");
  fclose($open);
}

$counter = $line[0]++;

?>

<?php echo $counter; ?>