private function generateMultipartFileHeader($name, $fileName, $contentType)
{
$header = "Content-Disposition: form-data; name=\"{$name}\"; filename=\"{$fileName}\"\r\n";
$header .= "Content-Type: {$contentType}\r\n";
$header .= "Content-Transfer-Encoding: binary\r\n\r\n";
return $header;
}