Zend\Diactoros\Request::getHeader PHP Méthode

    public function getHeader($header)
    {
        if (!$this->hasHeader($header)) {
            if (strtolower($header) === 'host' && ($this->uri && $this->uri->getHost())) {
                return [$this->getHostFromUri()];
            }
            return [];
        }
        $header = $this->headerNames[strtolower($header)];
        $value = $this->headers[$header];
        $value = is_array($value) ? $value : [$value];
        return $value;
    }