function do_post_request($url, $data, $optional_headers = null)  {     $params = array('http' => array(                  'method' => 'POST',                  'content' => $data               ));     if ($optional_headers !== null) {        $params['http']['header'] = $optional_headers;     }     $ctx = stream_context_create($params);     $fp = @fopen($url, 'rb', false, $ctx);     if (!$fp) {        throw new Exception("Problem with $url, $php_errormsg");     }     $response = @stream_get_contents($fp);     if ($response === false) {        throw new Exception("Problem reading data from $url, $php_errormsg");     }     return $response;  }