Deprecation: #64361 - Composer Class Loading

See forge#64361


TYPO3 CMS started integrating composer support and by that embracing PHP standards PSR-0 and PSR-4 for class loading that comes with composer. The old class loader is still present and registered and will handle loading extension classes that do not follow the above mentioned standards.

For the time being a pre-compiled composer class loader is shipped with the git repository, so that people using the TYPO3 sources directly from there can use it without requiring a composer install step.

It is possible however to do a composer install in the TYPO3 sources directory or a top level distribution directory to gain full control over class loading of your TYPO3 installation. This step is optional and currently requires thorough knowledge of composer and as such currently is only recommended for people familiar with this process.

Further technical details can be found in the documentation.


Third party libraries added to a TYPO3 installation via composer can immediately be used without further manual intervention. The classes cache for most core classes will be gone. Resolving classes is slowly shifted from a run time task - executed and monitored in every request - to an installation task with composer.

Affected installations

Some installations could be affected which were previously installed via composer, but now not properly updated using composer. And outdated Packages/Libraries/autoload.php file present in the system will lead to fatal errors.


If you previously installed TYPO3 via composer, make sure you perform a composer update command to reflect the current changes in your Packages folder.