protected function getRequestHeaders(array $headers)
{
$requestHeaders = '';
foreach ($this->headers as $name => $value) {
if (!isset($headers[$name])) {
$requestHeaders .= "{$name}: {$value}\r\n";
}
}
foreach ($headers as $name => $value) {
$requestHeaders .= "{$name}: {$value}\r\n";
}
return $requestHeaders;
}