How do I Persist the Logged in

Hi Constructers!

I made a Login Screen for my game using PHP and Mysql its working fine but how i persist the login.

Means that when game is start so the Player Login in the game and he/she play the game using Menu Screen then the Player exit the game and again play that game so the login should persist and the Player should be redirect to Menu Screen instead of Login screen. How its possible?

Thanks