Trouble with http upload in TWebCopy


I am trying to upload a small file via http with TWebCopy. This is the delphi code:

    with WebCopy.Items.Add do begin
      protocol := wpHTTPUpload;
      URL := '';
      TargetDir := 'c:\temp';
      TargetFileName := 'x.txt';

This is the php file:

$target_path = "user/";

$target_path = $target_path . basename( $_FILES['uploadedfile']['name']);

if(move_uploaded_file($_FILES['uploadedfile']['tmp_name'], $target_path)) {
    echo "The file ".  basename( $_FILES['uploadedfile']['name']).
    " has been uploaded";
} else{
    echo "There was an error uploading the file, please try again!";

There is no error returned, it simply does nothing. If I try to upload the file from a simple html frame, it works. This is the html frame:

<form enctype="multipart/form-data" action="getupdate.php" method="POST">
<input type="hidden" name="MAX_FILE_SIZE" value="100000" />
Choose a file to upload: <input name="uploadedfile" type="file" /><br />
<input type="submit" value="Upload File" />

What am I doing wrong?
Thanks in advance for your help.