public function addRole($role)
    {
        if ($this->instance instanceof \Phavour\Session\Storage) {
            if ($this->hasRole($role)) {
                return true;
            }
            if ($this->instance->isLocked()) {
                $this->instance->unlock();
            }
            $roles = $this->instance->get('roles');
            if (is_array($roles)) {
                $this->instance->set(
                    'roles', array_merge($roles, array($role)));
            } else {
                $this->instance->set('roles', array($role));
            }
            $this->instance->lock();
            return true;
        }

        return false;
    }