t3land

Glossary

Composer in TYPO3

The tool that manages and installs TYPO3, its extensions and their dependencies.

What Composer does

Composer is the dependency tool of the PHP world. You describe which packages a project needs and in which version ranges, and Composer makes sure a compatible combination is installed.

In TYPO3 that covers the core itself, every extension from the repository, and any other PHP libraries the project needs.

Why it matters at update time

The real gain shows up during an update. Composer knows the requirements of every extension and can say in advance whether a jump to a new TYPO3 version is possible, or which extension is in the way.

Without that information, every update begins with trial and error. With it, the list of problem cases is settled before anyone touches a file.

Reproducible installations

Composer writes the versions actually installed into a lock file. Put that file in the repository and every system ends up with exactly the same state.

That is what makes a preview environment meaningful. If different versions run there than in production, a successful test is not worth much.

Common questions

How does it differ from a classic installation?

In a classic installation, TYPO3 and the extensions sit as files in the project directory, installed through the Extension Manager. In a Composer installation they are listed as dependencies in a file, and Composer fetches matching versions.

The practical difference shows up at update time: Composer checks whether the versions you want fit together and refuses to install if they do not. Without Composer you only notice a conflict once the site is running.

Can an existing installation be converted?

Yes, but it is not a switch. For every installed extension you have to establish whether it exists as a Composer package, what its dependencies look like, and what happens to custom code that has been sitting outside so far.

The conversion is almost always worth it, because every subsequent update benefits. It should be planned as a work item of its own, though, rather than running along on the side of another project.

Installation still without Composer?

The conversion is not a switch, but it pays off at every update afterwards. We estimate the effort up front.

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