if you would like to send xml request to a server (lets say, making a soap proxy),
you have to set
<?php
curl_setopt($ch, CURLOPT_HTTPHEADER, Array("Content-Type: text/xml"));
?>
makesure you watch for cache issue:
the below code will prevent cache...
<?php
curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
curl_setopt($ch, CURLOPT_FRESH_CONNECT, 1);
?>
hope it helps ;)