Composer 101: A Quick Introduction and Installation Guide

Posted on September 11th, 2023

In the ever-evolving world of PHP development, managing dependencies and libraries efficiently is a key factor for successful projects. This is where Composer steps in. If you’re new to Composer or looking for a quick start, you’re in the right place.

Composer, developed by Nils Adermann and Jordi Boggiano, has been revolutionizing the world of PHP development since its initial release on March 1, 2012. This cross-platform package manager has become an indispensable tool for developers looking to simplify the management of dependencies and libraries in their PHP projects.

With its user-friendly approach and the flexibility it offers, Composer has gained immense popularity within the PHP community. It operates under the permissive MIT License and serves as an essential resource for PHP developers worldwide. To learn more or get started with Composer, visit their official website at

In this concise guide, we’ll walk you through the basics of Composer, from installation to getting started with your first project. Whether you’re a seasoned developer looking to adopt Composer or a newcomer exploring the PHP ecosystem, this article will help you learn the fundamental knowledge to start using Composer in your projects.

By the end of this guide, you’ll be on your way to smoother PHP development with Composer at your side.

First of all, make sure you have composer installed on your machine. If not, Follow our guide to install composer on a Linux machine.

Fundamentals of Composer

Once you have composer installed on your server or machine, You can start using composer. Before that, Let’s learn the fundamentals of composer. Composer is all about managing dependencies in your PHP projects efficiently. Here’s what you need to know:

The composer.json File:

At the core of Composer is the composer.json file. This JSON file serves as a manifest for your project’s dependencies. It lists all the libraries and packages required for your PHP application to run correctly. You define these dependencies within the composer.json file.

Here’s a simple example of what a composer.json file might look like:

  "require": {
    "monolog/monolog": "^2.0"

In this example, we specify that our project requires the “monolog/monolog” package at version 2.0 or higher. Similarly, If you check the composer.json file of a newly installed Laravel Project, You will see a lot of packages mentioned in the composer.json file. It allows Laravel to create different packages for different purposes and then use it when required using composer.

Dependency Resolution

When you run Composer commands like composer install or composer update, Composer analyzes your composer.json file and resolves the entire dependency tree for your project. It retrieves the specified packages and their dependencies, ensuring that they are compatible with each other. This process ensures that you get the correct versions of each package.


Composer simplifies the autoloading of classes in your PHP project. It generates an autoloader file that takes care of including the necessary files for classes when they are first used in your code. This eliminates the need for manual include or require statements for each class file.

Package Management

Composer interacts with the vast PHP ecosystem of packages hosted on Packagist. Packagist is the default package repository for Composer, containing thousands of open-source PHP packages that you can use in your projects. You specify the packages you want in your composer.json, and Composer fetches them from Packagist.

Dependency Lock File

Composer creates a composer.lock file to lock in the specific versions of packages used in your project. This ensures that every member of your team and any future deployments use the exact same versions of the packages. It helps maintain consistency across different environments and prevents unexpected issues due to package version discrepancies.

With these basic concepts in mind, you’re well-prepared to start using Composer in your projects. In the next section, we’ll guide you through creating a sample project and adding dependencies using Composer.

Getting Started with Composer

In this section, we will learn How to initialise composer in any PHP project to start using open-source libraries in your PHP project using composer. To begin, create a new directory for your PHP project if you haven’t already.

Initialize Composer

Open your terminal or command prompt, navigate to your project directory, and run the following command:

$ composer init

It will prompt you with a series of questions to configure your project. You can provide information about your project, such as its name, description, author, and license. Once you’ve answered these questions, Composer will generate a composer.json file based on your responses.

Install Dependencies

With your project initialized, you can now start adding dependencies. Let’s say you want to include the popular Monolog logging library.

To do this, simply run the following command, replacing monolog/monolog with the package you need:

$ composer require monolog/monolog

Composer will fetch the Monolog library from Packagist, resolve its dependencies, and add it to your project. You’ll notice updates to both your composer.json and composer.lock files.

Autoloading Classes

Composer’s autoloading feature is now in action. You can use Monolog classes in your code without worrying about manual includes or requires. For instance, you can create an instance of the logger like this:

use Monolog\Logger;
use Monolog\Handler\StreamHandler;

// Create a log channel
$log = new Logger('name');
$log->pushHandler(new StreamHandler('path/to/your.log', Logger::WARNING));

// Add records to the log
$log->warning('This is a warning message');
$log->error('This is an error message');

The autoloader takes care of including the necessary Monolog files in your project.

Update Dependencies

As the dependencies are managed by open-source contributors or companies, You need to update them as there might be security updates and patches and also the new features. In that case, just navigate to the project directory and execute the following command.

$ composer update

Composer will check for updates to your project’s dependencies, download any newer versions, and update the composer.lock file accordingly.

Autoloading in Composer

One of the standout features of Composer is its seamless autoloading of classes, making it a breeze to work with packages and libraries in your PHP projects.

When you add dependencies to your project using Composer, it generates an autoloader file for you. This file is usually named vendor/autoload.php and is placed in your project’s root directory. You don’t need to worry about including this file manually; Composer takes care of it.

Here’s how Composer’s autoloading works:

  • When you create an instance of a class from a Composer-managed package, PHP will first look for that class’s file.
  • If the class file is not yet loaded, Composer’s autoloader will kick in.
  • Composer’s autoloader will then analyze the class name, map it to the corresponding file path, and include the file.

This process happens automatically in the background, eliminating the need for you to write tedious include or require statements for each class file.

How to use Autoloading in a PHP Project

To use Composer’s autoloading, follow these steps.

Include the Composer autoloader at the beginning of your PHP script:

require 'vendor/autoload.php';

This line ensures that the autoloader is loaded and ready to work its magic. Now, Import the classes you need at the top of your PHP script using the use statement. For example:

use Monolog\Logger;
use Monolog\Handler\StreamHandler;

Now, you can use these classes in your code without worrying about manual includes.

Benefits of Autoloading

Composer’s autoloading offers several advantages:

  • Efficiency: Autoloading only loads classes when needed, reducing memory consumption and speeding up your application’s startup time.
  • Organization: Your code becomes cleaner and more organized since you don’t need to clutter it with include statements.
  • Ease of Maintenance: As your project grows, managing dependencies and classes becomes more straightforward thanks to Composer’s automated approach.

With Composer’s autoloading simplifying class loading in your PHP projects, you can focus on writing code without getting bogged down in the nitty-gritty details of dependency management. In the next section, we’ll briefly address common Composer issues and their solutions to ensure a smooth development experience.


In this quick journey into Composer, you’ve learned the essentials of this powerful tool for PHP development. Composer makes managing packages and libraries a breeze, simplifying your life as a PHP developer.

You’ve seen how to get Composer up and running, add dependencies to your project, and enjoy the magic of autoloading, which saves you from manually including class files.

Composer is your trusty companion on your PHP coding adventures. It streamlines your workflow, helps you manage dependencies effortlessly, and keeps your projects organized.

Now that you’re equipped with Composer basics, you’re ready to explore the vast world of PHP packages and create amazing projects. Happy coding!

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