Problem med update

Hejsa

Hvad er her fejlen?
Scriptet uploader ikke billeder men opdaterer tabellen. Her er min formular:

$id=$_GET[id];
echo"<form method='post' action='ndrbil2.php'>
Billede: <input type='file' name='file' id='searchsubmit'><br>
<input type='hidden' name='id' value='$id'>
<input type='submit' value='Ændr!' id='searchsubmit'>
";

og scriptet:




  $filename = 'billeder/' . basename($_FILES['file']['name']);


        if (move_uploaded_file($_FILES['file']['tmp_name'], $filename)) {
            echo "File is valid, and was successfully uploaded.";
        } else {
            echo 'DEBUG: Fra: ' . $_FILES['file']['tmp_name'] . ' til ' . $filename . '<br>';
            echo "Possible file upload attack!";
        }   

        $sql = ("update smykker set billede='$filename' where id='$id'");

        $res = mysql_query($sql) or die(mysql_error());