http://askubuntu.com/questions/705880/how-to-install-php-7

also for error “ZipArchive Library is missing or disabled”:
https://www.digitalocean.com/community/questions/php-7-0-ziparchive-library-is-missing-or-disabled

sudo apt-get install php7.0-cli php7.0-common libapache2-mod-php7.0 php7.0 php7.0-mysql php7.0-fpm php7.0-curl php7.0-gd php7.0-bz2 php7.0-zip