Open Source PHP Dependency Managers

Composer is a tool for dependency management in PHP, inspired by node's npm and ruby's bundler. It allows you to declare, manage and install the libraries on which your PHP project depends. Unlike most package managers, Composer manages on a per-project basis. It installs packages or libraries in a directory (e.g. vendor) inside your project and does not install anything globally. However, for convenience it does support a "global" project via the global command. Suppose your project depends on a number of libraries which in turn, depend on other libraries. Composer enables you to declare these libraries, finds out which versions of these packages you require, and installs them. You can then update all of your dependencies conveniently with just one command.

Symfony Dependency Injection is a core component of the Symfony framework that provides a flexible, service-oriented architecture for managing object dependencies. It follows the dependency injection pattern to improve modularity and testability in PHP applications. The component allows developers to define services, inject dependencies, and manage object lifecycles using configuration files or annotations.