Kan ikke sætte cookie

Jeg kan ikke få dette til at virke:

<?php
include("common.php");
include("db.php");

if((!$_POST[username]) || (!$_POST[password])) {
    include('error.php');
    exit();
}
$username = strtolower($_POST['username']);
$password = md5($_POST[password]);

$sql = mysql_query("SELECT * FROM users WHERE username='$username' AND password='$password' AND activated='1'");
$login_check = mysql_num_rows($sql);

if($login_check > 0){
    while($row = mysql_fetch_array($sql)){
    foreach( $row AS $key => $val ){
        $$key = stripslashes( $val );
    }
          setcookie("loged", "yes", mktime(0, 0, 0, 5, 14, 2000), $sitepath, $sitename);
          setcookie("username", "$username", mktime(0, 0, 0, 5, 14, 2000), $sitepath, $sitename);
          setcookie("user_level", "$user_level", mktime(0, 0, 0, 5, 14, 2000), $sitepath, $sitename);
          $session = uniqid('login_');
          header("Location: index.php");
    }
} else {
  include('error.php');
  exit();
}
?>

Hvad gør jeg galt?