How to Install Composer on Ubuntu 20.04

Introduction:

To follow this guide, you’ll need access to an Ubuntu 20.04 server as a sudo user.

If you don't already have a server. You can start off by ordering a Linux VPS

Step 1:

Start by updating your package manager cache and installing the required dependencies, including php-cli:

sudo apt update
sudo apt install php-cli unzip

Step 2:

Make sure you’re in your home directory, then retrieve the Composer installer using curl:

cd ~
curl -sS https://getcomposer.org/installer -o /tmp/composer-setup.php

Next, we’ll verify that the downloaded installer matches the SHA-384 hash for the latest installer found on the Composer Public Keys / Signatures page.

Using curl, fetch the latest signature and store it in a shell variable:

HASH=`curl -sS https://composer.github.io/installer.sig`

Now execute the following PHP code to verify that the installation script is safe to run:

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

You’ll see the following output:

Installer verified

The following command will download and install Composer as a system-wide command named composer, under /usr/local/bin:

sudo php /tmp/composer-setup.php --install-dir=/usr/local/bin --filename=composer

You’ll see output similar to this:

Output
All settings correct for using Composer
Downloading...

Composer (version 2.2.9) successfully installed to: /usr/local/bin/composer
Use it: php /usr/local/bin/composer

To test your installation, run:

composer

Output
   ______
  / ____/___  ____ ___  ____  ____  ________  _____
 / /   / __ \/ __ `__ \/ __ \/ __ \/ ___/ _ \/ ___/
/ /___/ /_/ / / / / / / /_/ / /_/ (__  )  __/ /
\____/\____/_/ /_/ /_/ .___/\____/____/\___/_/
                    /_/
Composer version 2.2.9 2022-03-15 22:13:37

Usage:
  command [options] [arguments]

Options:
  -h, --help                     Display this help message
  -q, --quiet                    Do not output any message
  -V, --version                  Display this application version
      --ansi                     Force ANSI output
      --no-ansi                  Disable ANSI output
  -n, --no-interaction           Do not ask any interactive question
      --profile                  Display timing and memory usage information
      --no-plugins               Whether to disable plugins.
  -d, --working-dir=WORKING-DIR  If specified, use the given directory as working directory.
      --no-cache                 Prevent use of the cache
  -v|vv|vvv, --verbose           Increase the verbosity of messages: 1 for normal output, 2 for more verbose output and 3 for debug
...

This verifies that Composer was successfully installed on your system and is available system-wide.