Which programming language/framework to choose?

I am planning to create multi-player game (for example chess) and I want it to be accessible from web browser and mobile devices (cross-platform game). Which programming language would You suggest if I want to write less code (re-usable code for web and mobile application). I would like the game to work on both Android and iOS (native application would be great, but that is not possible with one language, right?).

I am familiar with PHP, Python and basic C++ and does any of these is good for what I want? Also I think for backend NodeJS would be required to run multi-player logic (had few encounters with it).

I will appreciate all suggestions.