What is the difference between the commands 'composer install' and 'composer update', and in what situations are they used?

composer install and composer update are two main commands for managing dependencies in PHP projects using Composer.

• composer install installs dependencies specified in the composer.lock file. If composer.lock is absent, it is created based on composer.json. This command ensures that all developers and servers use the same library versions.

• composer update updates dependencies to the latest versions that satisfy the constraints in composer.json, and rewrites composer.lock with the new versions.

When to use:

• composer install — when deploying a project or when dependencies need to be installed without changes.
• composer update — when you need to update libraries to newer versions, for example, to get fixes or new features.

Important: composer update can lead to incompatibilities, so it should be used with caution and changes should be tested.