Fix session handling die to changes in PHP 7.1

 uphpCAS.php

@@ -14,6 +14,7 @@
    protected $serverUrl = '';
    protected $serviceUrl;
    protected $sessionName = 'uphpCAS-user';
    protected $sessionStarted = FALSE;
    protected $method = 'POST';
    protected $caFile = NULL;
    
@@ -112,6 +113,23 @@
        $this->caFile = $caFile;
    }
    
    public function session_start() {
        if($this->sessionStarted) {
            return TRUE;
        }
        if(version_compare(PHP_VERSION, '7.1.0', '<')) {
            @session_start();
        } else {
            if(!isset($_SESSION)) {
                if(!session_start()) {
                    throw new RuntimeException('Cannot start session');
                }
            }
        }
        $this->sessionStarted = TRUE;
        return TRUE;
    }
	
    public function loginUrl() {
        return $this->serverUrl.'/login?method='.$this->method
            .'&service='.urlencode($this->serviceUrl);
@@ -123,7 +141,7 @@
    }
    
    public function logoutLocal() {
        @session_start();
        $this->session_start();
        unset($_SESSION[$this->sessionName]);
    }
    
@@ -139,11 +157,12 @@
    }
    
    public function isAuthenticated() {
        $this->session_start();
        return isset($_SESSION[$this->sessionName]);
    }
    
    public function authenticate() {
        @session_start();
        $this->session_start();
        if($this->isAuthenticated()) {
            return $_SESSION[$this->sessionName];
        } elseif(isset($_REQUEST['ticket'])) {