TYPO3 Core

The 1-2-3 install tool loads the dbal extension on demand if some php extensions like pdo are loaded. It adds dbal to extList and forces a reload. The core autoloader creates a cache entry depending on the current loaded extensions. So the cache must be cleared before redirect to force a recalculation of the autoloader class list. This prevents a fatal error 'class tx_dbal_querycache not found' during install.