Phaser Physics - Stop sideways velocity

stopSidewaysVelocity.js

/**
 * Negate sideways velocity on an object being acted upon by a Phaser physics engine.
 * The primary use for this is to simulate vehicle movement by negating "drift" when the vehicle turns.
 * @param {Phaser.Sprite} sprite The sprite whose sideways velocity you want to negate
 */
function stopSidewaysVelocity(sprite) {
	// Recycle the same object to conserve memory
	if(!stopSidewaysVelocity.sideways) {
		stopSidewaysVelocity.sideways = {};
	}

	var body     = sprite.body;
	var velocity = body.velocity;
	var rotation = body.rotation + Math.PI / 2;
	var sideways = stopSidewaysVelocity.sideways;

	sideways.x = Math.cos(rotation);
	sideways.y = Math.sin(rotation);

	var dot_product = velocity.x * sideways.x + velocity.y * sideways.y;

	velocity.x = sideways.x * dot_product;
	velocity.y = sideways.y * dot_product;
}

Run it every frame in your sprite's update function, preferably after any logic to apply new velocity.