What is Composer? How to Install for Mac, Linux, and Windows?
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16 May 2023

What is Composer? How to Install for Mac, Linux, and Windows?

In modern PHP development, managing dependencies and libraries is an essential part of the workflow. It can be a challenging task to manually download, install, and update multiple libraries and their dependencies. This is where Composer, a dependency manager for PHP, comes to the rescue. In this article, we will explore the features and benefits of Composer and provide step-by-step instructions for installing and using it effectively.

What is Composer?

Composer is a command-line tool for managing dependencies in PHP projects. It simplifies the process of including external libraries or packages into your PHP applications. With Composer, you can declare the libraries your project depends on and let it handle the installation, autoloading, and updating of those libraries.

Why Use Composer?

Using Composer offers several advantages for PHP developers:

1. Dependency Management Made Easy

Composer allows you to declare the libraries your project depends on and automatically installs the specified versions along with their dependencies. It takes care of managing the entire dependency tree, ensuring that all required libraries are present and compatible.

2. Centralized Package Repository

Composer utilizes the Packagist repository, which serves as a central hub for thousands of PHP libraries and packages. This vast collection of packages covers a wide range of functionalities, making it easy to find and include the right libraries for your project.

3. Version Constraint Management

Composer provides flexible version constraint management, allowing you to define which versions of a package your project supports. You can specify precise version numbers or use wildcard expressions to define ranges, ensuring that your project stays compatible with the required dependencies.

4. Autoloading Support

Composer generates an optimized autoloader file for your project, eliminating the need for manual inclusion of files. This autoloader ensures that the required classes are automatically loaded when needed, simplifying the development process and improving performance.

5. Dependency Locking

Composer allows you to generate a lock file that records the exact versions of all installed dependencies, including their transitive dependencies. This lock file ensures that everyone working on the project uses the same versions of libraries, guaranteeing consistency across different environments and preventing unexpected compatibility issues.

Installing Composer

Linux / Unix / macOS

To get started with Composer, follow these steps to install it on your system:

Step 1: Check PHP Version

Before installing Composer, make sure you have PHP installed on your system. Open a terminal or command prompt and run the following command to check your PHP version:

php -v

Composer requires PHP 5.3.2 or later to run. If you have an older version of PHP, consider upgrading to a compatible version.

Step 2: Download Composer

Composer provides an installer script that you can use to download and install it on your system. Run the following command in your terminal or command prompt:

php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"

This command will download the installer script, composer-setup.php, into your current directory.

Step 3: Verify the Installer

To ensure the integrity of the installation script, you can verify its authenticity by comparing the hash checksum. Run the following commands to download the expected hash checksum and verify the installer:

php -r "if (hash_file('sha384', 'composer-setup.php') === '55ce33d7678c5a611085589f1f3ddf8b3c52d662cd01d4ba75c0ee0459970c2200a51f492d557530c71c15d8dba01eae') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"

If the installer is verified, you can proceed to the next step.

Step 4: Install Composer

To install Composer, run the following command:

php composer-setup.php

This command will install Composer globally on your system and make it accessible via the composer command.

Step 5: Remove Setup File

After the installation is complete, you can remove the setup file by running the following command:

php -r "unlink('composer-setup.php');"

Congratulations! You have successfully installed Composer on your system.

You have the flexibility to store the Composer PHAR file in any location you prefer. If you choose to place it in a directory that is included in your system's PATH environment variable, you will be able to access it globally from anywhere on your system. Additionally, on Unix systems, you have the option to make the Composer PHAR file executable, allowing you to invoke it without directly using the PHP interpreter.

Once you have successfully run the installer according to the instructions provided on the Composer download page, you can execute the following command to relocate the composer.phar file to a directory that is included in your system's PATH:

sudo mv composer.phar /usr/local/bin/composer

By doing so, you will be able to run the Composer command globally, regardless of your current working directory.


Follow these steps to install Composer on your Windows machine using the Composer Installer:

Step 1: Download the Installer

  • Visit the Composer download page in your web browser.
  • Click on the "Composer-Setup.exe" link to download the installer file.

Step 2: Run the Installer

  • Locate the downloaded "Composer-Setup.exe" file.
  • Double-click on the installer file to run it and start the installation process.

Step 3: Follow the Installation Wizard

  • The Composer Installer will open a setup wizard.
  • Follow the on-screen instructions to proceed with the installation.
  • Choose the desired installation options when prompted.

Step 4: Complete the Installation

  • Once the installation is complete, Composer will be installed with the latest version on your Windows machine.
  • The installer will automatically configure the PATH environment variable, enabling you to access the composer command from any directory in the command line.

Note: It is important to close your current terminal and open a new one after the installation. This ensures that the updated PATH configuration takes effect.

Congratulations! You have successfully installed Composer on your Windows machine using the Composer Installer. You can now use Composer to manage dependencies for your PHP projects.

Using Composer

Now that Composer is installed, let's explore some common commands and workflows:

Initializing a Project

To start using Composer in your PHP project, navigate to the project's root directory in your terminal and run the following command:

composer init

This command will interactively guide you through creating a composer.json file, where you can define your project's dependencies, autoload settings, and other configurations.

Adding Dependencies

To add a dependency to your project, you need to update the composer.json file. You can manually add the required packages and their versions, or you can use the require command. For example, to add the popular library monolog, run the following command:

composer require monolog/monolog

Composer will resolve the dependencies and download the required packages into the vendor directory.

Autoloading Classes

Composer provides a convenient autoloading mechanism that automatically loads the required classes in your project. To utilize autoloading, make sure to include the Composer-generated autoloader file in your PHP scripts:

require 'vendor/autoload.php';

This line ensures that the necessary classes are loaded when they are referenced in your code.

Updating Dependencies

To update your project's dependencies, including their transitive dependencies, use the following command:

composer update

Composer will check for updates in the composer.json file and install the latest compatible versions of the packages.

Generating the Autoloader

If you make changes to the autoloading settings in the composer.json file, you need to regenerate the autoloader file. Use the following command to do so:

composer dump-autoload

Composer will regenerate the autoloader file based on the updated configuration.

Using Composer Scripts

Composer allows you to define custom scripts in the composer.json file. These scripts can be used to automate certain tasks in your project. For example, you can define a script to run unit tests or perform code analysis. To execute a script, use the following command:

composer run-script <script-name>

Replace <script-name> with the name of the script defined in the composer.json file.


Composer is an indispensable tool for managing dependencies in PHP projects. With its powerful features and easy-to-use interface, it simplifies the process of including external libraries and ensures that your project's dependencies are well-managed. By following the installation instructions and understanding the usage patterns outlined in this article, you can harness the full potential of Composer and streamline your PHP development workflow.