Composer Update vs. Composer Install: When Should You Use Each?

Distinguishing Composer Update from Composer Install

In the world of PHP dependency management, Composer plays a crucial role. Understanding the subtle differences between two of its commands, composer update and composer install, is essential for efficient dependency handling.

Composer Update

Composer update serves the purpose of updating dependencies to the latest versions specified in composer.json. If a package is declared with a constraint like "0.9.*" and a newer release (e.g., "0.9.2") becomes available, composer update will upgrade the dependency to the latest compatible version.

Key steps of composer update:

• Parses composer.json to determine required dependencies
• Removes obsolete packages from the installation
• Fetches the latest versions of required packages
• Installs the updated dependencies
• Updates composer.lock file to reflect the updated package versions

Composer Install

Composer install, on the other hand, focuses on installing all the dependencies based on the specifications defined in the composer.lock file. It doesn't perform any updates or version checks.

Steps involved in composer install:

• Checks whether composer.lock exists; if not, it runs composer update first
• Reads composer.lock and installs packages accordingly

When to Use Each Command

• Composer update: Typically used during development to update dependencies and ensure the latest versions are used.
• Composer install: Commonly employed during deployment or in testing environments to install specific dependencies based on the locked-in versions in composer.lock.

By understanding these differences, developers can effectively manage PHP dependencies, keeping their projects up-to-date while maintaining stability in deployment environments.

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