Composer is a dependency manager for PHP (similar to npm for Node.js or pip for Python). Composer will pull in all the required PHP packages your project depends on and manage them for you.

This  tutorial provides the steps necessary to install Composer on Debian 9  systems. We will also cover how to use Composer to create and manage PHP  projects.


Before continuing with this tutorial, make sure you are logged in as a user with sudo privileges and you have PHP installed on your Debian 9 system.

Installing Composer

Follow the steps below to install Composer on Debian systems:

First update the packages index and install the necessary packages with the following commands:

sudo apt update

Once the dependencies are installed, use the php cli toll to download the Composer installation script:

php -r "copy('', 'composer-setup.php');"

The command above will download the composer-setup.php file in the current working directory.

We’ll verify the script data integrity by comparing the script SHA-384 hash with the latest installer hash found on the Composer Public Keys / Signatures page.

Run the following wget command to download the expected signature of the latest Composer installer  from the Composer’s Github page and store it in a variable named HASH:

HASH="$(wget -q -O -"

To verify that the installation script is not corrupted copy and paste the following code into your console:

php -r "if (hash_file('SHA384', 'composer-setup.php') === '$HASH') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"

If the hashes match, you’ll see the following output:

Installer verified

If the hashes don’t match you will see Installer corrupt. In this case, you will need to redownload the Composer installation script and double check the value of the $HASH variable with echo $HASH. Once the installer is verified, you can continue with the next step.

The following command will install Composer in the /usr/local/bin directory:

sudo php composer-setup.php --install-dir=/usr/local/bin --filename=composer
All settings correct for using Composer

Composer (version 1.8.5) successfully installed to: /usr/local/bin/composer
Use it: php /usr/local/bin/composer

At this point you  have Composer installed on your Debian system. It is installed as a  system-wide command and it will be available for all users.

To verify the installation simply type:


The command above will print the Composer’s version, commands, and arguments.

/ ____/___  ____ ___  ____  ____  ________  _____
/ /   / __ \/ __ `__ \/ __ \/ __ \/ ___/ _ \/ ___/
/ /___/ /_/ / / / / / / /_/ / /_/ (__  )  __/ /
\____/\____/_/ /_/ /_/ .___/\____/____/\___/_/
Composer version 1.8.5 2019-04-09 17:46:47

    command [options] [arguments]

If you want to use a per-project Composer installation run the following command php composer-setup.php which will create a file named composer.phar in your current working directory. You can use the composer by running ./composer.phar <command>.

Getting Started with Composer

Now that you have Composer is installed on your Debian system we will show you how to create a PHP project with Composer.

Start by creating a a directory which will be the project root and hold the composer.json file. This file describes your PHP project including the PHP dependencies and other metadata.

Create the project directory and switch to it with:

mkdir ~/my-first-composer-project

Next, we’ll initialize a new composer.json file using the composer require <package name> command and specify the package we want to download. In this example,  we will create a sample application that will print the current time  using a package called carbon.

Run the following command to initialize a new composer.json file and install the carbon package:

composer require nesbot/carbon
Using version ^1.34 for nesbot/carbon
./composer.json has been created
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Installing symfony/polyfill-mbstring (v1.9.0): Downloading (100%)         
  - Installing symfony/translation (v3.4.17): Downloading (100%)         
  - Installing nesbot/carbon (1.34.0): Downloading (100%)         
symfony/polyfill-mbstring suggests installing ext-mbstring (For best performance)
symfony/translation suggests installing symfony/config
symfony/translation suggests installing symfony/yaml
symfony/translation suggests installing psr/log-implementation (To use logging capability in translator)
Writing lock file
Generating autoload files

Composer will create a composer.json file and download and install carbon and all its dependencies.

If you list your project’s directory with the ls command, you will see that it contains two files composer.json and composer.lock, and a vendor directory.

ls -l
-rw-r--r-- 1 black users   60 Oct 16 21:02 composer.json
-rw-r--r-- 1 black users 6851 Oct 16 21:02 composer.lock
drwxr-xr-x 5 black users 4096 Oct 16 21:02 vendor

  • vendor - the directory where the project dependencies are stored.
  • composer.lock - file containing a list of all installed packages including the version of the packages.
  • composer.json - file describing the PHP project and all PHP dependencies.

You can search the Composer repository Packagist for PHP packages.

Composer provides autoload capabilities which allow us to use PHP classes without the need to require or include the files.

Create a file named testing.php and paste the following code:


require __DIR__ . '/vendor/autoload.php';

use Carbon\Carbon;

printf("Now: %s", Carbon::now());


Let’s analyze the code line by line.

In the first line after the opening php tag we are including the vendor/autoload.php file that was automatically generated by Composer. This file will autoload all the required libraries.

Next, we are aliasing Carbon\Carbon as Carbon and in the last line we are printing the current time using the Carbon now method.

Run the script by typing:

php testing.php

The output should look something like below:

Now: 2018-10-16 21:08:45

3. Updating Packages with Composer

To update the PHP packages, simply run:

composer update

The command above will check for newer versions of the installed packages and if a newer version is found and the version constraint match with the one specified in the composer.json, Composer will update the package.


You  have learned how to install Composer on your Debian 9 machine. We have  also shown you how to use Composer to create a basic PHP project. To  find more information about Composer visit the official Composer documentation page.

If you have any questions, please leave a comment below.