How to make player restrict of boundries only left right not up and down in phaser js game?

You can set the custom world bounds, with the function this.physics.world.setBounds(...). Here a link to the documentation.

So, you just would have to put this line, into your code:

`this.physics.world.setBounds(0, 0, widthOfTheGame, heightOfTheGame, true, true, false, true);`.

in the create function.

following the documenttation setBounds(x, y, width, height [, checkLeft] [, checkRight] [, checkUp] [, checkDown])

The third false is for the world-bounds-top, and so no colliding should occure.