Deprecation: #98283 - PHP Constant TYPO3_mainDir 

See forge#98283

Description 

The PHP Constant TYPO3_mainDir which is defined as typo3/ has been marked as deprecated.

Impact 

Accessing the constant will stop working in TYPO3 v13. No deprecation warning is thrown, but the Extension Scanner will detect any usage in your installation.

Affected installations 

TYPO3 installations with custom third-party extensions using the constant directly, which is highly unlikely.

Migration 

It is recommended to use the BackendEntryPointResolver class when needing to direct to the TYPO3 Backend. All other common APIs such as the Backend Router already calculate the path automatically anyway.