composer update ubuntu 20.04

First, update the package manager cache by running:

sudo apt update
 
Next, run the following command to install the required packages:

sudo apt install php-cli unzip

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

cd ~
curl -sS https://getcomposer.org/installer -o 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. To facilitate the verification step,
you can use the following command to programmatically obtain the latest hash from the Composer page and store it in a shell variable:

HASH=`curl -sS https://composer.github.io/installer.sig`
 
If you want to verify the obtained value, you can run:

echo $HASH

Now execute the following PHP code, as provided in the Composer download page,
to verify that the installation script is safe to run:

php -r "if (hash_file('SHA384', 'composer-setup.php') === '$HASH') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
 
You’ll see the following output:

Output
Installer verified

If the output says Installer corrupt, you’ll need to download the installation 
script again and double check that you’re using the correct hash.
Then, repeat the verification process. When you have a verified installer,you can continue.

To install composer globally, use the following command which will download and install Composer as a system-wide command named composer, under /usr/local/bin:

sudo php 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 1.10.5) successfully installed to: /usr/local/bin/composer
Use it: php /usr/local/bin/composer
To test your installation, run:

$composer