Comparing Express, Phoenix, Rails, Flask, Grails and... PHP?

hello.php

<?php
echo json_encode(array('hello'=>'world!'));
?>

hello.py

from flask import Flask
from flask import jsonify
app = Flask(__name__)

@app.route("/")
def hello():
  return jsonify(hello="world!")

if __name__ == "__main__":
  app.run()

hello_controller.rb

class HelloController < ApplicationController
  def index
    render json:{"hello"=>"world!"}
  end
end

HelloController.groovy

class HelloController {
  def index() {
    render([ hello:"world!" ] as grails.converters.JSON)
  }
}

index.js

var express = require('express');
var router = express.Router();

router.get('/', function(req, res) {
  res.json({hello:'world!'});
});

module.exports = router;

page_controller.ex

defmodule HelloPhoenix.PageController do
  use Phoenix.Controller
  alias Poison, as: JSON
  plug :action

  def index(conn, _params) do
    json conn, JSON.encode!(%{hello: "world!"})
  end
end

Just a note: rails s in the development environment runs a single-threaded server that has debugging tools enabled. It's not close to production performance or behavior.