Cookie::expire PHP Method

    public function expire()
    {
        if (!isset($_SESSION[$this->_index]) || !is_array($_SESSION[$this->_index]) || empty($_SESSION[$this->_index])) {
            return;
        }
        unset($_SESSION[$this->_index]);
        // Calling session_destroy triggers the Session::destroy function which removes the entire session
        // from the database. To prevent logout issues between functionality that relies on $_SESSION, such
        // as Symphony authentication or the Members extension, only delete the $_SESSION if it empty!
        if (empty($_SESSION)) {
            session_destroy();
        }
    }

 /**
  * This function determines whether an there is a currently logged in
  * Author for Symphony by using the `$Cookie`'s username
  * and password. If an Author is found, they will be logged in, otherwise
  * the `$Cookie` will be destroyed.
  *
  * @see core.Cookie#expire()
  */
 public function isLoggedIn()
 {
     // Ensures that we're in the real world.. Also reduces three queries from database
     // We must return true otherwise exceptions are not shown
     if (is_null(self::$_instance)) {
         return true;
     }
     if ($this->Author) {
         return true;
     } else {
         $username = self::Database()->cleanValue($this->Cookie->get('username'));
         $password = self::Database()->cleanValue($this->Cookie->get('pass'));
         if (strlen(trim($username)) > 0 && strlen(trim($password)) > 0) {
             $author = AuthorManager::fetch('id', 'ASC', 1, null, sprintf("\n\t\t\t\t\t\t\t`username` = '%s'\n\t\t\t\t\t\t", $username));
             if (!empty($author) && Cryptography::compare($password, current($author)->get('password'), true)) {
                 $this->Author = current($author);
                 self::Database()->update(array('last_seen' => DateTimeObj::get('Y-m-d H:i:s')), 'tbl_authors', sprintf(" `id` = %d", $this->Author->get('id')));
                 // Only set custom author language in the backend
                 if (class_exists('Administration')) {
                     Lang::set($this->Author->get('language'));
                 }
                 return true;
             }
         }
         $this->Cookie->expire();
         return false;
     }
 }