tl_content::checkAccessToElement PHP Method

    protected function checkAccessToElement($id, $pagemounts, $blnIsPid = false)
    {
        if ($blnIsPid) {
            $objPage = $this->Database->prepare("SELECT p.id, p.pid, p.includeChmod, p.chmod, p.cuser, p.cgroup, a.id AS aid FROM tl_article a, tl_page p WHERE a.id=? AND a.pid=p.id")->limit(1)->execute($id);
        } else {
            $objPage = $this->Database->prepare("SELECT p.id, p.pid, p.includeChmod, p.chmod, p.cuser, p.cgroup, a.id AS aid FROM tl_content c, tl_article a, tl_page p WHERE c.id=? AND c.pid=a.id AND a.pid=p.id")->limit(1)->execute($id);
        }
        // Invalid ID
        if ($objPage->numRows < 1) {
            throw new Contao\CoreBundle\Exception\AccessDeniedException('Invalid content element ID ' . $id . '.');
        }
        // The page is not mounted
        if (!in_array($objPage->id, $pagemounts)) {
            throw new Contao\CoreBundle\Exception\AccessDeniedException('Not enough permissions to modify article ID ' . $objPage->aid . ' on page ID ' . $objPage->id . '.');
        }
        // Not enough permissions to modify the article
        if (!$this->User->isAllowed(BackendUser::CAN_EDIT_ARTICLES, $objPage->row())) {
            throw new Contao\CoreBundle\Exception\AccessDeniedException('Not enough permissions to modify article ID ' . $objPage->aid . '.');
        }
    }