protected function determineHeaders()
    {
        $params = $this->getServerParams();
        $headers = [];
        
        foreach ($params as $key => $value) {
            $name = $this->serverParamKeyToHeaderName($key);
            
            if (isset($name) && is_string($value)) {
                $headers[$name] = [$value];
            }
        }
        
        return $headers;
    }