See https://www.digitalocean.com/community/questions/how-to-upgrade-from-php-v-5-5-9-to-v-5-6

1sudo apt-get install -y python-software-properties 2sudo add-apt-repository -y ppa:ondrej/php 3sudo apt-get update -y 4sudo apt-get install -y $(apt-cache pkgnames | grep php7.1|tr "\n" " ") See https://www.vultr.com/docs/how-to-install-and-configure-php-70-or-php-71-on-ubuntu-16-04