Debian 6 & 7

PHP 7.0 can be installed using the Dotdeb repository:

Add these two lines to your /etc/apt/sources.list file, replacing <distribution> with either squeeze, wheezy, or jessie:

deb http://packages.dotdeb.org <distribution> all
deb-src http://packages.dotdeb.org <distribution> all

Add the GPG key:

wget https://www.dotdeb.org/dotdeb.gpg
sudo apt-key add dotdeb.gpg

Install PHP 7:

sudo apt-get update
sudo apt-get install php7.0

The full list of available packages can be found here: http://packages.dotdeb.org/pool/all/p/php7.0/