private function getFromHeader(ServerRequestInterface $request)
{
$headers = call_user_func_array('array_merge', array_column($this->formats, 1));
$mime = $this->negotiateHeader($request->getHeaderLine('Accept'), new Negotiator(), $headers);
if ($mime !== null) {
foreach ($this->formats as $format => $data) {
if (in_array($mime, $data[1], true)) {
return $format;
}
}
}
}