Depending on your target date and algorithms needed, I would say stick with PHP as your front end and move your backend to either a Go based service or a Pytho

Depending on your target date and algorithms needed, I would say stick with PHP as your front end and move your backend to either a Go based service or a Python one. The single binary feature of Go makes deployment really easy. And the standard library has everything you need to do an API. I chose the gin framework in my case with the standard html/template. The front end uses knockoutjs. If you need some specialized library like machine learning or natural language processing, I would choose Python as there are many great libraries out there.