fejl i uploadscript

Hvorfor virker dette uploadscript ikke... jeg får hele tiden beskeden: ERROR da filen åbenbart ikke blir uploadet...

////////// KODE /////////////

if($_FILES['fil']) {
$filename = "bannere_img/$id.jpg";

$fra = $_FILES['fil']['name'];

$ext = strtolower(end(explode(".", $_FILES['fil']['name'])));

if($ext == "jpg" || $ext == "jpeg") {

$til = "bannere_img/" . $id . "_temp" . "." . $ext;

move_uploaded_file($fra, $til);

if(file_exists($til)) { rename($til, $filename); dbInsert("update Bannere set img='$filename' where id=$id"); } else { echo "ERROR"; }} else { echo "skal være jpg"; }}

////////// FORM /////////////

<form action="?page=Edit.Banner&id=<? echo $id; ?>" method=post>
Ny fil: <input type="file" name="fil">
<input type=submit value="upload billede">