static

<?php

class login{

    public static $user;

    public static function verificalogin(){
        echo "O usuario ".self::$user." esta logado<br>";
    }
        public function sairsistema(){
            echo "O usuario ".self::$user." saiu do sistema";
        }
    }

login::$user = "admin";
login::verificalogin();
login::sairsistema();