src/CacheStorage.php
private function fetchVary(RequestInterface $request)
    {
        $key = $this->getVaryKey($request);
        $varyHeaders = $this->cache->fetch($key);

        return is_array($varyHeaders) ? $varyHeaders : [];
    }
private function fetchVary(RequestInterface $request)
    {
        $key = $this->getVaryKey($request);
        $varyHeaders = $this->cache->fetch($key);

        return is_array($varyHeaders) ? $varyHeaders : [];
    }
private function fetchVary ( RequestInterface $ request ) { $ key = $ this -> getVaryKey ( $ request ) ; $ varyHeaders = $ this -> cache -> fetch ( $ key ) ; return is_array ( $ varyHeaders ) ? $ varyHeaders : [ ] ; }
Fetch the Vary headers associated with a request, if they exist.

Only responses, and not requests, contain Vary headers. However, we need
to be able to determine what Vary headers were set for a given URL and
request method on a future request.

@param RequestInterface $request The Request to fetch headers for.

@return array An array of headers.
Fetch the Vary headers associated with a request if they exist .