[NeXT]

I'd use something like this:

<? 
$f=fopen("counter.dat","a+");
flock($f,LOCK_EX); 
$count=fread($f,100);
@$count=$count+1;
ftruncate($f,0);
fwrite($f,$count);
fflush($f);
flock($f,LOCK_UN);
fclose($f);
echo $count;
?>

I'm just learning php but I think this is the simplest script you can get..I may be wrong.