How to create a basic rating system

"DTD/xhtml1-transitional.dtd">


if ( (!isset($_POST['submit'])) ) { ?>
echo $_SERVER['PHP_SELF']; ?>" method="post">

} else {
$rate = isset ($_POST['rate']) ? $_POST['rate'] : 0;
$filename = "ratings";
$alreadyRated = false;
$totalRates = 0;
$totalPoints = 0;

$ip = getenv('REMOTE_ADDR');

// Read the result file
$oldResults = file('results/'.$filename.'.txt');

// Summarize total points and rates
foreach ($oldResults as $value) {
$oneRate = explode(':',$value);
// If our IP is in the list then set the falg
if ($ip == $oneRate[0]) $alreadyRated = true;
$totalRates++;
$totalPoints += $oneRate[1];
}

// If our rating is valid then append it to the result file
if ((!$alreadyRated) && ($rate > 0)){
$f = fopen('results/'.$filename.".txt","a+");
fwrite($f,$ip.':'.$rate."\n");
fclose($f);
$totalRates++;
$totalPoints+=$rate;
}

echo "Actual rating from $totalRates rates is: "
.substr(($totalPoints/$totalRates),0,3)."
";

// Display the actual rating
for ($i=0;$i<round(($totalPoints/$totalRates),0);$i++){
echo "";
}
} ?>