Convert little php script to lua script

Hello, I implemented some logic in php to cache page urls in redis. As it is slow, I want to convert this php script directly to a lua script to implement in openresty (nginx redis module). At the end of the script, if the url is not in cache, the module redirect the request to the backend. I would need to return an additional query string to inform that we need to create or not the cache for that specific url.