TYPO3 Core

When logging with the Core Logging API, one has to use \TYPO3\CMS\Core\Log\LogManager->getLogger() to get an instance of a logger.

Adding an interface \TYPO3\CMS\Core\Log\LogManagerInterface will enable you to ship an alternative 3rd party LogManager instance. Given the LogManager is added to a class using dependency injection, this would make it possible to use Monolog for logging without touching any class.