Composer

Composer is the standard dependency manager for PHP. It manages project-level dependencies (libraries and packages) by reading a composer.json file and downloading the required packages from Packagist (the default package repository) or other configured sources. It is an essential tool for modern PHP development and is widely used in the hosting ecosystem.

For hosting providers, Composer matters because a large portion of modern PHP applications require it. Laravel, Symfony, Drupal 8+, and many WordPress plugins and themes use Composer for dependency management. When customers deploy these applications, Composer needs to be available on the server to install and update their dependencies.

Composer handles dependency resolution automatically. If package A requires package B version 2.x and package C requires package B version 2.1+, Composer calculates the correct version of package B that satisfies both requirements. This eliminates the manual headache of tracking nested dependencies across complex application stacks.

The autoloader generated by Composer (vendor/autoload.php) provides PSR-4 and PSR-0 compliant class autoloading. This means PHP applications can use any installed package without manual require or include statements. Virtually all modern PHP frameworks rely on Composer's autoloader.

Most shared hosting providers now include Composer pre-installed and accessible via SSH. cPanel servers typically have it available at /usr/local/bin/composer. For managed hosting platforms, Composer is often integrated into deployment pipelines to install dependencies automatically during code deployment.

Composer also supports scripts and hooks that run during install and update operations, private package repositories for proprietary code, and platform requirements checking to verify the server meets application prerequisites before installation.