Contao\ModuleBooknav::getBookPages PHP Method

    protected function getBookPages($intParentId, $groups, $time)
    {
        $objPages = \PageModel::findPublishedSubpagesWithoutGuestsByPid($intParentId, $this->showHidden);
        if ($objPages === null) {
            return;
        }
        foreach ($objPages as $objPage) {
            $_groups = \StringUtil::deserialize($objPage->groups);
            // Do not show protected pages unless a front end user is logged in
            if (!$objPage->protected || is_array($_groups) && count(array_intersect($groups, $_groups)) || $this->showProtected) {
                $this->arrPages[$objPage->id] = $objPage;
                if ($objPage->subpages > 0) {
                    $this->getBookPages($objPage->id, $groups, $time);
                }
            }
        }
    }