[NHern031]

The .NET CORE is now open source and cross platform. Cross platform compatibility with the exact same source code, and the killer features/speed of C# makes its my personal choice for a server-side language. I would like to add that C# devs are not cheap and also seem to be slightly more limited in today's market compared to PHP devs.

[sjellis]

If you are running .NET code in production on a non-Windows platform today, then you and your team are probably braver and more willing to work around issues than most. I hope that running .NET code on Linux becomes the common case, but I suspect that we are still a couple of years away from that.

[ZenoArrow]

It might not be exactly what you had in mind as 'in production', but it's probably worth noting that Unity uses Mono as a core component, and it seems to be fairly popular on non-Windows platforms.

https://github.com/Unity-Technologies