How to post xml data in drupal_http_request? I have curl code of it
Seeing how drupal_http_request() is used in _xmlrpc(), something like this should do it.

// The path to send the request
$url = "http://example.com/API_PATH_HERE";
// Example of valid xml code;
$xmlrequest = "&lt;showId&gt;0&lt;/showId&gt;&lt;tag&gt;123&lt;/tag&gt;";

$response = drupal_http_request($url, array(
  'headers' =&gt; array('Content-Type' =&gt; 'text/xml'),
  'data' =&gt; $xmlrequest,
  'method' =&gt; 'POST',
  'timeout' =&gt; 10
));
// If there is no error return data
if (empty($response-&gt;error)) {
  $result['xml'] = $response-&gt;data;
}