As a new developer joining a PHP project using Composer, I need to understand how Composer ensures everyone works with the same dependency versions. Explain the purpose of `composer.json` and `composer.lock` files, and how `composer install` and `composer update` commands are used to maintain consistent project dependencies for team collaboration.
Navigate to the 'Basic usage' documentation page on getcomposer.org. Locate and read the sections detailing the purpose and usage of `composer.json` and `composer.lock`. Understand how `composer install` and `composer update` commands interact with these files to manage dependencies. Identify the recommended practices for committing `composer.json` and `composer.lock` to version control for team consistency. Synthesize all gathered information into a comprehensive explanation.
The explanation clearly states that `composer.json` defines project dependencies with version constraints (the desired dependencies). The explanation clearly states that `composer.lock` records the exact versions of all installed dependencies, ensuring reproducible builds and consistency across environments. The explanation details that `composer install` uses `composer.lock` (if present) to install exact versions, or `composer.json` to resolve and install dependencies (creating `composer.lock`) if the lock file is absent. The explanation details that `composer update` resolves the latest compatible versions based on `composer.json` and then updates `composer.lock` with these new exact versions. The explanation states that both `composer.json` and `composer.lock` should be committed to version control to ensure consistent dependency versions for all collaborators and deployment environments.