Question on Collision

[Gamma]

How do you check if an object or the player specifically touches the 'WorldBounds'. In the phaser engine, you can set an object so that it can only stay in the 'WorldBound' by adding the line:

ObjectGoesHere.body.collideWorldBounds = true;

But how would I detect that the certain object has touched one the sides or the upper and bottom portions of the game window?

 

Also, I notice as I increase the velocity or gravity of an object, if a certain object falls from the sky at high speeds it does not touch the platform, instead it skips to to touching and bouncing off the bottom of the screen. That is where this question originates from.