Does it work to deploy a React project to Netlify while the Laravel backend is deployed in Heroku?

php reactjs laravel heroku netlify

Yes, it's possible you just have to add Functions to your front app.

Tutorial React APP to Netlify :https://www.netlify.com/blog/2016/07/22/deploy-react-apps-in-less-than-30-seconds/

Function API example :https://functions-playground.netlify.com/

Hope this helps.