Add isAuthenticated() method to check whether user is already logged in

 uphpCAS.php

@@ -71,9 +71,13 @@
        die();
    }
    
    public function isAuthenticated() {
        return isset($_SESSION['uphpCAS-user']);
    }
	
    public function authenticate() {
        session_start();
        if(isset($_SESSION['uphpCAS-user'])) {
        if($this->isAuthenticated()) {
            return $_SESSION['uphpCAS-user'];
        } elseif(isset($_REQUEST['ticket'])) {
            $user = $this->verifyTicket($_REQUEST['ticket']);