TYPO3 Exception 1596980032


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InvalidArgumentException: A cache identifier was not set

When debuging the corresponding cache.definition might look like this:

'' => array('groups' => array('pages', 'all'))

This error can break the backend and frontend.


Before TYPO3 version 10 it was common that the variable $_EXTKEY was replaced automatically by the extension key of the corresponding extension.

This has changed and the variable either has to be defined or the extension key automatically applied.

As the variable $_EXTKEY was undefined, the array key for the cache definition was empty.

The error was therefore caused by an incomplete extension-update.


Search in all extensions for usage of $_EXTKEY in the file ext_localconf.php.

If the variable is used but not defined in that file, define it in the beginning or replace it by the extension key.