TYPO3 v10: Init Frontend-environment for use in CLI- or BE-context

typo3_init_fe.php

protected function initFrontend() {
    $siteId = 1;
    $pageId = 1219;
    $typeNum = 0;
    if (!is_object($GLOBALS['TT'])) {
        $GLOBALS['TT'] = new \TYPO3\CMS\Core\TimeTracker\TimeTracker;
        $GLOBALS['TT']->start();
    }

    $context = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Context\Context::class);
    $siteFinder = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Site\SiteFinder::class);
    $site = $siteFinder->getSiteByRootPageId($siteId);
    $siteLanguage = $site->getDefaultLanguage();
    $request = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Http\ServerRequest::class);
    $GLOBALS['TYPO3_REQUEST'] = $request;

    $pageArguments = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Routing\PageArguments::class, $pageId, $typeNum, []);
    $frontendUserAuthentication = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Frontend\Authentication\FrontendUserAuthentication::class);

    $GLOBALS['TSFE'] = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Frontend\Controller\TypoScriptFrontendController::class,  $context, $site, $siteLanguage, $pageArguments, $frontendUserAuthentication);
    $GLOBALS['TSFE']->determineId();

    // needed since otherwise overriding $_SERVER-variables will not work because of a cache in GeneralUtility
    \TYPO3\CMS\Core\Utility\GeneralUtility::flushInternalRuntimeCaches();
}