Phly\Http\MessageTrait::filterHeaders PHP Method

    private function filterHeaders(array $originalHeaders)
    {
        $headerNames = $headers = [];
        foreach ($originalHeaders as $header => $value) {
            if (!is_string($header)) {
                continue;
            }
            if (!is_array($value) && !is_string($value)) {
                continue;
            }
            if (!is_array($value)) {
                $value = [$value];
            }
            $headerNames[strtolower($header)] = $header;
            $headers[$header] = $value;
        }
        return [$headerNames, $headers];
    }