I haven't kept a watch on other languages for a while now, but I am pretty well versed with Ruby, so I would probably go with Ruby and Sinatra.

Any compiled language - except for Rust ;)

The two things I cannot sacrifice anymore are:

1. Static types
2. Compiles down to native binary

Although I could sacrifice binary compilation if I'm working in Kotlin (but it's not ideal).

Current languages that I think are feasible:

Go

Swift

D

Languages I would avoid (for my personal projects):

Python

Ruby

I go with PHP for some very simple reasons.

1) It's ubiquitous. Try finding hosting that doesn't provide it! The problem with EVERY other language out there is half the hosts you even ASK about another language stack -- node.js, ruby, whatever -- will tell you "No, we don't allow that" and won't even give you the common courtesy of explaining why. That limits your audience for anything you build AND your choices on where to host. Whilst I do maintain my own set of VPS, not everyone has the money for a VPS or dedicated, much less the skill -- and to assume your project will only ever be maintained by you? Utter foolishness.

2) Documentation. php.net is some of the BEST documentation out there for a free language. When I try to use other languages unless they've been around for decades finding GOOD CLEAR documentation is a joke. Maybe I got spoiled by Borland giving you multiple massive books in box sets in the late '80's and early '90's, but what passes for documentation of languages like Python, Perl, Ruby, or even JavaScript is a pathetically useless JOKE!

3) Community. Finding knowledgeable help is EASY since again, the language is everywhere. With full stack JS two thirds the people out there who know JavaScript still seem unaware it can be used server side; mixed with a stream of bile and vitriol from the accessibility minded since people take the concept of "full stack JavaScript" WAY too far! With Python half the time you get "why would you do that" the other half the time you get "what's that?". Ruby are so needlessly cryptic in syntax people seem to waste more time on playing with syntactic sugar than they do writing useful software rendering questions about ACTUALLY doing things moot.

With PHP you go into a forums and ask "How do I do this?" and you'll get five different answers, three of them being clean, clear, simple, and easy to follow.

---

Now, those are the advantages. The disadvantages are many, but also dwindling. Speed concerns as of PHP 7 are nonexistent as it now pulls ahead of Java and .NET on many tasks. MORE so when the JIT compilation branch is in use which when that goes from experimental to mainstream is going to be a huge game changer!

Apart from that, security is the biggest issue but let's be brutally frank on that... is server side JavaScript REALLY going to be any better on that? Of course not since it has a looser scope and can dynamically include non-bytecoded scripting JUST like PHP.

I mean, the only thing I'd really change to properly and FINALLY secure PHP would be to make it so include/require can only operate on files with the .php extension, all other file operations would be blocked from being able to operate on files with the .php extension, and that include/require break scope and do not allow code to be directly run. (aka the only thing valid in includes should be functions or classes)

When those are the "big complaints" that's easily dismissed compared to train wreck languages like Ruby and Python. After four decades of programming I still look at both of those and go "what the *** is in the kool-aid?!?".

But what do I know, if I had full control I'd probably be using ADA or Oberon; given I worship at the throne of all things Wirth.

Erlang/Golang

Go FTW.

I'm undecided between Go, Rust, Elixir, Erlang or Clojure

C# / Ruby, Python

Elixir

PHP, not because I particularly like it (sorry PHP..) but because it's the only other server language I'm totally comfortable with and because the Laravel framework is wonderful for big apps.

Though if I was to stray outside of my comfort zone and have the time to experient and learn as I go... I'd fancy giving Go or Rust a try.

And if I had all the time in the world... Haskell!

Go

Rust. I already plan to switch a few things over, because I like the safety and structure of Rust :) Good thing we have Neon, so I can even write .node modules in Rust, so I don't have to separate my programs completely :D

C#