Вы ищете что-то вроде этого:
$process = curl_init($host);
curl_setopt($process, CURLOPT_HTTPHEADER, array('Content-Type: application/xml', $additionalHeaders)); //<-- update to reflect your content-type
curl_setopt($process, CURLOPT_HEADER, 1);
curl_setopt($process, CURLOPT_USERPWD, $username . ":" . $password); // <-- you probably don't need that
curl_setopt($process, CURLOPT_TIMEOUT, 30);
curl_setopt($process, CURLOPT_POST, 1);
curl_setopt($process, CURLOPT_POSTFIELDS, $payloadName);
curl_setopt($process, CURLOPT_RETURNTRANSFER, TRUE);
$return = curl_exec($process);