Keyboard#Keyboard

The Keyboard class monitors keyboard input and dispatches keyboard events.

Note: many keyboards are unable to process certain combinations of keys due to hardware limitations known as ghosting.
See http://www.html5gamedevs.com/topic/4876-impossible-to-use-more-than-2-keyboard-input-buttons-at-the-same-time/ for more details.

Also please be aware that certain browser extensions can disable or override Phaser keyboard handling.
For example the Chrome extension vimium is known to disable Phaser from using the D key. And there are others.
So please check your extensions before opening Phaser issues.