TYPO3 Core

PHP 8.1 throws an exception on saving a new entry with includes a field of type "select" and renderType = "selectCheckbox". (didn't test other renderTypes)

Exception is `Illegal offset type in isset or empty` in file web/typo3/sysext/backend/Classes/Utility/BackendUtility.php on Line 681.

It appears that $typeNum contains the array of the selected items if the element is new. If it is edited and saved, it includes a string with the values comma separated.

An array is apparaently not allowed in this isset() condition.

I am not sure why there is this difference if the element is new or edited. But it is already in this format when it arrives in the ServerRequest and as far as i have seen, it is never converted into a comma separated string in the dataHandler.

first checking if it is an array does fix the issue and the entry is correctly created in the database.