Using PHP backend with React Application

I have a react app and I run npm run build to generate a build package that I upload to S3. let's say www.test.com/build/

but I have a PHP backend that should be responsible for serving the index.html (from www.test.com/index.html)

since there's no connection with the S3 bucket and the PHP app I don't know how to deal with the hashed names in the react app

I can't generate the build package without the hashes because I will lose the cache buster.

what are some good practices to work with react apps and backend apps. In this case is PHP but I think the problem should be the same with a NodeJS backend hosted in a different server.

I'm using AWS CodePipeline to build the react app (npm run build) and the php app (composer install)

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