FTPing a zip file

[D Elkins]

I am trying to write a small web interface to allow users to upload a
zip file to our server. Below is code:
//The form
<FORM action="ftp_upload.php" method=post
enctype="multipart/form-data">
<input type="hidden" name="MAX_FILE_SIZE" value="10000">
<input type="file" name="userfile"> <br>
<input type="submit" name="Upload File" value="Upload File">
</FORM>
//ftp_upload.php
// set up basic connection
$conn_id = ftp_connect(serverinfo);

// login with username and password
$login_result = ftp_login($conn_id, username, password);

// check connection
if ((!$conn_id) || (!$login_result))
{
echo "FTP connection has failed!";
echo "Attempted to connect to $ftp_server for user
$ftp_user_name";
exit;
}
else
{
echo "Connected to ".$ftp_server.", for user ".
$ftp_user_name."<br>";
}

$source_file = $_FILES['userfile']['tmp_name'];

// upload the file
$upload = ftp_put($conn_id, $somedir.$userfile_name, $source_file,
FTP_BINARY);

// check upload status
if (!$upload)
{
echo "<br>FTP upload has failed!";
}
else
{
echo "<br>Uploaded $source_file to $ftp_server as
$destination_file";
}

// close the FTP stream
ftp_quit($conn_id);

?>
All of this works fine except for a .zip file in which case I get the
following message:

Warning: error opening none in ftp_upload.php on line 72

This is the ftp_put line.

Any help would be greatly appreciated .......