I am able to do it in PHP as well. Here is the Code:
I have PHP 5.6.3
$data1 = array( 'file2' => new CurlFile('C:/temp/Test_1.doc', 'application/msword'),
'file1' => new CurlFile('C:/temp/Test_1.xml', 'text/xml')
);
$mydata = http_build_query($postfields);
$ch = curl_init();
curl_setopt($ch, CURLOPT_VERBOSE, 0);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-type: multipart/form-data"));
curl_setopt($ch, CURLOPT_POSTFIELDS, $data1);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'PUT');
curl_setopt($ch, CURLOPT_URL, $signedURI);
$responseStream = curl_exec($ch);
$header = curl_getinfo( $ch );
if ($header['http_code'] == 200)
print_r("File uploaded successfully");
saveFile($responseStream, $outPath);