src/CacheStorage.php
private function normalizeVary(ResponseInterface $response)
    {
        $parts = AbstractMessage::normalizeHeader($response, 'vary');
        sort($parts);

        return $parts;
    }
private function normalizeVary(ResponseInterface $response)
    {
        $parts = AbstractMessage::normalizeHeader($response, 'vary');
        sort($parts);

        return $parts;
    }
private function normalizeVary ( ResponseInterface $ response ) { $ parts = AbstractMessage :: normalizeHeader ( $ response , 'vary' ) ; sort ( $ parts ) ; return $ parts ; }
Return a sorted list of Vary headers.

While headers are case-insensitive, header values are not. We can only
normalize the order of headers to combine cache entries.

@param ResponseInterface $response The Response with Vary headers.

@return array An array of sorted headers.
Return a sorted list of Vary headers .