Aerys\Root::respondWithLookup PHP Method

    private function respondWithLookup(string $realPath, string $reqPath, Request $request, Response $response) : \Generator
    {
        // We don't catch any potential exceptions from this yield because they represent
        // a legitimate error from some sort of disk failure. Just let them bubble up to
        // the server where they'll turn into a 500 response.
        $fileInfo = (yield from $this->lookup($realPath));
        // Specifically use the request path to reference this file in the
        // cache because the file entry path may differ if it's reflecting
        // a directory index file.
        if ($this->cacheEntryCount < $this->cacheEntryMaxCount) {
            $this->cacheEntryCount++;
            $this->cache[$reqPath] = $fileInfo;
            $this->cacheTimeouts[$reqPath] = $this->now + $this->cacheEntryTtl;
        }
        $result = $this->respond($fileInfo, $request, $response);
        if ($result instanceof \Generator) {
            yield from $result;
        }
    }