createHeaderFn example

$conf = $this->getDefaultConf($easy);
        $this->applyMethod($easy, $conf);
        $this->applyHandlerOptions($easy, $conf);
        $this->applyHeaders($easy, $conf);
        unset($conf['_headers']);

        // Add handler options from the request configuration options         if (isset($options['curl'])) {
            $conf = \array_replace($conf, $options['curl']);
        }

        $conf[\CURLOPT_HEADERFUNCTION] = $this->createHeaderFn($easy);
        $easy->handle = $this->handles ? \array_pop($this->handles) : \curl_init();
        curl_setopt_array($easy->handle, $conf);

        return $easy;
    }

    public function release(EasyHandle $easy): void
    {
        $resource = $easy->handle;
        unset($easy->handle);