file upload problem

[waza]

Hey,
I got a problem with the upload of files.
At my page I have this:

<form method="post" action="portfolio.php">
<input type="hidden" name="do" value="doupload">
<input type="file" name="file01" />
<input type="submit" value="Upload">
</form>

In portfolio.php I have this:

PHP Code:

if($_POST['do']=="doupload"){
$vbulletin->input->clean_array_gpc("f",array(
"file01" => TYPE_FILE,
));
die(print_r($vbulletin->GPC['file01']));
} 


But it returns an empty array:
array( ) 1

Does anybody see what I'm doing wrong?
thx,
seba

I found it
I had to add:
enctype="multipart/form-data"
to the form tag.