Hello people of this forum.
Here is what you normally do when you wish to add a callback function for a keyboard key:
aKey = game.input.keyboard.addKey(Phaser.KeyCode.A);
aKey.onDown.add(AKeyPressed, this);
In my case I wish to add same callback function when a new game frame is updated. (Yes, I know there is a reserved update function for this stuff, but this is not how I want to use it)