PHP cURL HTTP PUT

I am trying to create a HTTP PUT request with cURL and I can’t make it work. I’ve read many tutorials but none of them actually worked. Here’s my current code:

$filedata = array('metadata' => $rdfxml);
$ch = curl_init($url);
$header = "Content-Type: multipart/form-data; boundary='123456f'";
curl_setopt($ch, CURLOPT_VERBOSE, 1);
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "PUT");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, array($header));
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($filedata));
$returned = curl_exec($ch);

if (curl_error($ch))
{
    print curl_error($ch);
}
else
{
    print 'ret: ' .$returned;
}

I’ve also tried using PHP PEAR but got the same result. The problem is that the repository says that no metadata has been set. I really need help! Thanks!