PHP CURL PUT to Spreedly Core

curl_put_spreedly.php

<?php

$apiLogin = 'Ll6fAtoVSTyVMlJEmtpoJV8Shw5';
$apiSecret = 'RKOCG5D8D3fZxDSg504D0IxU2XD4Io5VXmyzdCtTivHFTTSylzM2ZzTWFwVH4ucG';
$paymentToken = 'N2V9GWfTgYv4jXAz2vcc4T3i8f6';

$url = 'https://spreedlycore.com/v1/payment_methods/' . $paymentToken . '/retain.xml';

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_USERPWD, $apiLogin . ':' . $apiSecret);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "PUT");
curl_setopt($ch, CURLOPT_POSTFIELDS, "");

// Attempt to set content-length to 0 to workaround nginx error...
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-type: application/xml'));          

curl_exec($ch);
curl_close($ch);