composer

Interactively create a composer.json file

$ composer init

$ composer require [user/package]

$ composer install

$ composer remove [user/package]

$ composer update

$ composer update --lock

$ composer why-not [user/package]

$ composer self-update

composer [options] [command] [arguments]

--help (-h)
    Displays help information.

--quiet (-q)
    Do not output any message.

--verbose (-v|-vv|-vvv)
    Increase verbosity of messages: 1 for normal output, 2 for more verbose output and 3 for debug.

--version (-V)
    Display this application version.

--ansi
    Force ANSI output.

--no-ansi
    Disable ANSI output.

--no-interaction (-n)
    Do not ask any interactive question.

--profile
    Display timing and memory usage information.

--working-dir (-d)
    If specified, use the given directory as working directory.

--no-plugins
    Whether to disable plugins.

--no-cache
    Disables the cache.

--optimize-autoloader (-o)
    Convert PSR-0/4 autoloading to classmap to get faster autoloader.

--classmap-authoritative (-a)
    Autoload classes from the classmap only. Implicitly enables `--optimize-autoloader`.

--apcu-autoloader
    Use APCu to cache found/not-found classes.

--ignore-platform-reqs
    Ignore platform requirements (php, ext-*, etc.).

--ignore-platform-reqs-dev
    Ignore platform requirements in require-dev (php, ext-*, etc.).

--prefer-stable
    Prefer stable versions.

--prefer-lowest
    Prefer lowest versions.

--only-root-dependencies
    Ignore root package dependencies.

--no-scripts
    Skips the execution of all scripts defined in composer.json file.

Composer is a dependency management tool for PHP. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you. Composer deals with "packages" (libraries) but it manages them on a per-project basis, installing them in a directory (e.g. 'vendor') inside your project. By default, Composer installs packages from Packagist, which is the main Composer package repository. It is highly customizable allowing you to define your own repositories.

It simplifies the process of including external libraries and ensuring you have the correct versions. By defining dependencies in a `composer.json` file, Composer handles fetching, installing, and updating these dependencies, freeing developers from manually managing library versions and potential conflicts.

Composer relies on having PHP installed and configured correctly on your system. It requires internet access to download packages from remote repositories (like Packagist).

The `composer.json` file is central to Composer's operation. It specifies project metadata (name, description, authors), dependencies (`require` and `require-dev`), autoloading rules, scripts, and other configurations.

By default Composer installs all dependencies in a `vendor` directory. The autoloader generated by Composer allows easy access to these dependencies without needing to manually `require` each file.

The `composer update` command updates your dependencies to the latest versions allowed by the version constraints specified in `composer.json` and updates the `composer.lock` file. `composer install` installs the versions specified in `composer.lock` or, if it does not exist, resolves and installs dependencies specified in the `composer.json`.

Composer was created by Nils Adermann and Jordi Boggiano and first released on March 1, 2012. It was inspired by other dependency management tools like Bundler (Ruby) and npm (Node.js). Composer quickly gained popularity within the PHP community, becoming the de facto standard for managing dependencies in PHP projects. Its use has contributed to better code organization, reusability, and collaboration within the ecosystem.

npm(1), apt(8)