Sends the error associated with the given Exception as a plain PHP response.
This method uses plain PHP functions like header() and echo to output the response.
\Exception|FlattenException $exception An \Exception instance:
public function sendPhpResponse($exception) {
  if (!$exception instanceof FlattenException) {
    $exception = FlattenException::create($exception);
  }
  header(sprintf('HTTP/1.0 %s', $exception
    ->getStatusCode()));
  foreach ($exception
    ->getHeaders() as $name => $value) {
    header($name . ': ' . $value, false);
  }
  echo $this
    ->decorate($this
    ->getContent($exception), $this
    ->getStylesheet($exception));
}