explaingit

composer/composer

Analysis updated 2026-06-20

★ 29,400PHPAudience · developerComplexity · 2/5Setup · easy

TLDR

The standard package manager for PHP, declare which libraries your project needs, and Composer automatically finds compatible versions, downloads them, and sets up your code to use them.

Mindmap

mindmap
  root((Composer))
    What it does
      Manages PHP packages
      Resolves version conflicts
      Sets up autoloading
    How it works
      composer.json config file
      Packagist.org registry
      PHP runtime
    Use cases
      Start a new PHP project
      Add or update libraries
      Share packages publicly
    Audience
      PHP developers
      Web app builders
      Framework users
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Code map

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filefunction / class

What do people build with it?

USE CASE 1

Start a new PHP web project and use Composer to pull in frameworks like Laravel or Symfony and all their dependencies in one command.

USE CASE 2

Add a new library (like a payment SDK or email sender) to an existing PHP project without manually downloading files.

USE CASE 3

Update all packages in a PHP project to their latest compatible versions while ensuring nothing breaks by checking version constraints.

What is it built with?

PHPPackagist

How does it compare?

composer/composerfilamentphp/filamentblueimp/jquery-file-upload
Stars29,40030,59930,774
LanguagePHPPHPPHP
Setup difficultyeasymoderateeasy
Complexity2/53/52/5
Audiencedeveloperdeveloperdeveloper

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · easy Time to first run · 5min

Requires PHP 7.2.5+ already installed, Composer itself is a single file download and runs from the command line immediately.

Not specified in the explanation.

In plain English

Composer is a dependency manager for PHP, the programming language widely used for web applications. The problem it solves is coordinating which external code packages a project needs, finding compatible versions, and installing them automatically, rather than requiring developers to download and manage each piece manually. You declare the libraries your project depends on in a configuration file, and Composer figures out a set of versions that all work together, then downloads them. It also handles autoloading, meaning it sets up PHP so your code can find and use those libraries without extra configuration. Public packages are distributed through Packagist.org, private hosting is available through Private Packagist. The tool is written in PHP itself and requires PHP version 7.2.5 or higher for its latest release. An older long-term-support version supports PHP from 5.3.2 through 8.1. It optionally uses command-line tools such as git, unzip, and tar to handle different archive formats. Anyone writing a PHP project would use Composer. It is the standard way PHP developers manage external libraries, roughly analogous to npm for JavaScript or pip for Python. You would reach for it at the start of a project to pull in the packages you need, and again when updating those packages or adding new ones.

Copy-paste prompts

Prompt 1
I'm starting a new PHP project and want to use Composer to manage dependencies. Walk me through creating a composer.json file, adding a library like Guzzle for HTTP requests, and running composer install.
Prompt 2
My PHP project uses Composer and I need to update all packages to their latest compatible versions. Show me the commands and explain what composer.lock is for.
Prompt 3
I want to add Composer autoloading to my custom PHP classes so I don't need to manually require each file. Show me how to configure the autoload section in composer.json.
Prompt 4
How do I publish my own PHP library to Packagist so other developers can install it with Composer? Walk me through the steps from creating the package to submitting it.

Frequently asked questions

What is composer?

The standard package manager for PHP, declare which libraries your project needs, and Composer automatically finds compatible versions, downloads them, and sets up your code to use them.

What language is composer written in?

Mainly PHP. The stack also includes PHP, Packagist.

What license does composer use?

Not specified in the explanation.

How hard is composer to set up?

Setup difficulty is rated easy, with roughly 5min to a first successful run.

Who is composer for?

Mainly developer.

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