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;    }