What is the difference between the commands composer install and composer update?

The composer install command installs the project dependencies according to the versions fixed in the composer.lock file. If this file exists, Composer guarantees that it will install exactly the versions of packages specified there, ensuring environment stability.

The composer update command updates dependencies to the latest versions that satisfy the constraints specified in composer.json. At the same time, composer.lock is updated with the new package versions. This is used when you want to get the latest library updates.

In summary:

• composer install — installs dependencies from composer.lock (fixed versions).
• composer update — updates dependencies and rewrites composer.lock.

Example:

composer install   # installs versions from composer.lock
composer update    # updates dependencies and composer.lock