ot_typo3/ot_templating/Classes/ViewHelpers/RootPage/GetIdViewHelper.php

<?php

namespace Opentalent\OtTemplating\ViewHelpers\RootPage;

use Closure;
use Opentalent\OtTemplating\Page\OtPageRepository;
use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3Fluid\Fluid\Core\Rendering\RenderingContextInterface;
use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper;

/**
 * Viewhelper to retrieve the Id of the current site root page
 * Call it in fluid templates with:
 *
 *     {namespace ot=Opentalent\OtTemplating\ViewHelpers}
 *
 *     {ot:rootPage.getId()}
 *
 * @package Opentalent\OtTemplating\ViewHelpers
 */
class GetIdViewHelper extends AbstractViewHelper
{
    /**
     * -- This method is expected by Fluid --
     * Renders the content as html
     *
     * @param array $arguments
     * @param Closure $renderChildrenClosure
     * @param RenderingContextInterface $renderingContext
     * @return int|null
     */
    public static function renderStatic(
        array $arguments,
        Closure $renderChildrenClosure,
        RenderingContextInterface $renderingContext
    ) {
        $pageUid = $GLOBALS['TSFE']->id;

        $pageRepository = GeneralUtility::makeInstance(OtPageRepository::class);
        return $pageRepository->getRootPageFor($pageUid)['uid'];
    }
}