Usta phpcilere bir soru

<?php
session_start();
$sid = session_id();
$_SESSION['gid'] = $_GET['id'];

$fp = fopen("test.txt", "a+");
fwrite($fp, "1: ".$_GET['id']." ($sid)\n");
fclose($fp);
?>
<iframe width=0 height=0 frameborder=0 src=bak2.php?id=<?=$sid ?>></iframe>

<?php
session_start();
$sid = session_id();

if ($sid == $_GET['id']) {
  $fp = fopen("test.txt", "a+");
  fwrite($fp, "2: ".$_SESSION['gid']." ($sid)\n");
  fclose($fp);
}

session_destroy();
?>

<?php
$site = file_get_contents("http://uye.adres");
if (preg_match("/Burda Uyelik Kodu Falan/s", $site)) {
  echo "Aferin durust uye";
}
else {
  uye_imha("site_id_falan");
  echo "Vay cakal";
}
?>