PHP7 on Debian8 - andreydiveev/wiki GitHub Wiki

https://linux-notes.org/ustanovka-php-7-php-fpm-s-nginx-1-9-v-debian-8/

echo "deb http://packages.dotdeb.org jessie all" >> /etc/apt/sources.list && echo "deb-src http://packages.dotdeb.org jessie all" >> /etc/apt/sources.list
cd /usr/local/src && wget https://www.dotdeb.org/dotdeb.gpg && apt-key add dotdeb.gpg
apt-get update
apt-get install php7.0*