Just to let people out there know, on my windows 2000 server running Apache and php i was returned 0 not -1 for directories.
foreach ($dir_list as $item)
{
if(ftp_size($conn_id, $item) == "0")
{
echo "<br>Directory:: ".$item;
} else {
echo "<br>File:: ".$item;
}
}
This outputs a list of the remote directory and indicates which items are directories and which are files.