PHP is serverside, you could not have used it "for browser" except on the web server. You would use it for your hybrid app in exactly the same way - on the web server, and not inside your hybrid app. In your hybrid app, you would have an AJAX call, for example, contacting your server for authentication and persistence. It does not need to be PHP, but it does need to be a serverside executable.
You need the server primarily because it makes no sense to even ask if the user is logged in unless there is somewhere they can be logged into