# If the Suhosin extension is enabled, you need to 
# allow execution of PHARs in your php.ini:
suhosin.executor.include.whitelist = phar

# To globally install the PHAR:
$ wget https://phar.phpunit.de/phpunit-6.5.phar
$ chmod +x phpunit-6.5.phar
$ sudo mv phpunit-6.5.phar /usr/local/bin/phpunit
$ phpunit --version

# You may also use the downloaded PHAR file directly:
$ wget https://phar.phpunit.de/phpunit-6.5.phar
$ php phpunit-6.5.phar --version