Physics#enable()

This will create a default physics body on the given game object or array of objects.
A game object can only have 1 physics body active at any one time, and it can't be changed until the object is destroyed.
It can be for any of the physics systems that have been started:

Phaser.Physics.Arcade - A light weight AABB based collision system with basic separation.
Phaser.Physics.P2JS - A full-body advanced physics system supporting multiple object shapes, polygon loading, contact materials, springs and constraints.
Phaser.Physics.NINJA - A port of Metanet Softwares N+ physics system. Advanced AABB and Circle vs. Tile collision.
Phaser.Physics.BOX2D - A port of https://code.google.com/p/box2d-html5
Phaser.Physics.MATTER - A full-body and light-weight advanced physics system (still in development)
Phaser.Physics.CHIPMUNK is still in development.

If you require more control over what type of body is created, for example to create a Ninja Physics Circle instead of the default AABB, then see the
individual physics systems enable methods instead of using this generic one.