Breaking: #72368 - TYPO3 Constants removed 

See forge#72368

Description 

The PHP constants TYPO3_enterInstallScript and TYPO3_cliMode and the global variable $GLOBALS['TYPO3_AJAX'] which were used when a TYPO3 Request was initialized have been removed. They have been replaced by an alternative to use the TYPO3_REQUESTTYPE constant at the very beginning of each TYPO3 request.

Impact 

Checking for the mentioned constants and global variable have no effect anymore and may lead to unexpected behaviour.

If not checked if the constant even was defined, the application will stop immediately.

Affected Installations 

Any installation which uses a third-party extension using these constants.

Migration 

Use TYPO3_REQUESTTYPE & TYPO3_REQUESTTYPE_CLI or TYPO3_REQUESTTYPE & TYPO3_REQUESTTYPE_INSTALL instead.