<?php
$filename = 'counter.txt';
$ip_filename = 'ip.txt';

function inc_count() {
  $ip = $_SERVER['REMOTE_ADDR'];
  global $filename, $ip_filename;

  if (!in_array($ip, file($ip_filename, FILE_IGNORE_NEW_LINES))) {
  $current_value = (file_exists($filename)) ? file_get_contents($filename) : 0;
  file_put_contents($ip_filename, $ip."\n", FILE_APPEND);
  file_put_contents($filename, ++$current_value);
 }

}
inc_count();

?>