actualizar a versão do compositor
composer self-update
comando de auto-actualização do compositor
composer self-update
actualização do compositor do php
php composer.phar update
actualizar a versão do PHP do compositor
php7.3 -f /usr/local/bin/composer update
actualizar o compositor
To update composer command just find location of composer.phar and update as:
where composer #Retrieves you location of your composer.phar
cd path_to_composer.phar #Move to directory with composer.phar
php composer.phar self-update #Update your composer