Hi there,

In case that you’ve installed composer with apt already you might have to remove the package first and then follow the steps from the tutorial:

• Remove the current installation:

sudo apt remove composer

• Install the latest version:

php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
php -r "if (hash_file('sha384', 'composer-setup.php') === '756890a4488ce9024fc62c56153228907f1545c228516cbf63f885e036d37e9a59d27d63f46af1d4d07ee0f76181c7d3') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
sudo php composer-setup.php --install-dir=/usr/local/bin --filename=composer
php -r "unlink('composer-setup.php');"

Let me know how it goes.
Regards,
Bobby