Fetching backend user in TYPO3 v9 not possible

Question

I worked with older TYPO3 versions (< v9)

I am not able to fetch the logged in backend user in my frontend extension. In earlier TYPO3 versions I was able to do that.

Now when I logged in in TYPO3 backend and ask for it now it won't work anymore.

My approach is:

$context = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Context\Context::class);
$be_username = $context->getPropertyFromAspect('backend.user', 'username');

I am getting an empty string. I know that backend user might be not available for FE. But I need to check on him.

Thank you for any suggestions.

Answer 1

If you want to find out if a Backend user is currently logged in, then the code is exactly right (you don't even need to check on the username).

$context = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Context\Context::class);
$isLoggedIn = $context->getPropertyFromAspect('backend.user', 'isLoggedIn');

However, if you do this in your extension in a Plugin, that is cacheable ("USER" cObject, or a "non-cacheable action" in an Extbase Plugin), this information could be cached, which can lead to serious. sideffects.

In general, you should only check for a backend user in Frontend-related events, PSR-15 middlewares or hooks from TSFE, not in plugins/cObjects etc. unless you really know what you are doing.

All the best, Benni-