eZ\Bundle\EzPublishRestBundle\Features\Context\RestClient\BuzzDriver::setHeader PHP Method

    public function setHeader($header, $value)
    {
        if (is_array($value)) {
            $value = implode(';', $value);
        }
        // Buzz can only add/append header, so we need to (re-)set all headers
        $headers = $this->unFormatHeaders($this->getRequest()->getHeaders());
        $headers[$header] = $value;
        $this->getRequest()->setHeaders($headers);
    }