Phaser Movement -- Multiple Keys

script.js

var game = new Phaser.Game(
  200, //The width in pixels
  200, //The height in pixels
  Phaser.AUTO, //The render system
  "phaser", //The element
  {
    preload: preload, // The preload function
    create: create, // The create function
    update: update // The update function
  }
);

// Create the variable outside of any one function scope
var sprite;

function preload() {}

function create() {
  sprite = game.add.sprite(
    50, // The x position
    50, // The y position
    'sprite' // The image cache-key
  );
}

function update() {
  if (game.input.keyboard.isDown(Phaser.Keyboard.LEFT)) {
    sprite.x -= 4; // Move left
  }
  if (game.input.keyboard.isDown(Phaser.Keyboard.RIGHT)) {
    sprite.x += 4; // Move right
  }
  if (game.input.keyboard.isDown(Phaser.Keyboard.UP)) {
    sprite.y -= 4; // Move up
  }
  if (game.input.keyboard.isDown(Phaser.Keyboard.DOWN)) {
    sprite.y += 4; // Move down
  }
}