What is Composer in PHP?

Composer is the dependency manager of PHP. It downloads the libraries (called packages) that your project needs, and keeps them updated. Packages come from a website called Packagist.

You write the needed packages in a file named composer.json. Composer installs them in the vendor folder and also creates an autoloader, so you do not need to write require for every class.

Command	What it does
composer init	Creates a composer.json file
composer require vendor/package	Installs a package and adds it to composer.json
composer install	Installs all packages listed in composer.lock
composer update	Updates packages to the latest allowed version
composer dump-autoload	Rebuilds the autoloader

<?php
// One line loads every installed package
require __DIR__ . "/vendor/autoload.php";
?>

Composer is used by almost all modern PHP frameworks like Laravel and Symfony. Do not upload the vendor folder to Git, only composer.json and composer.lock.

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