Add this to the file /etc/apt/sources.list:
deb http://packages.dotdeb.org jessie all
deb-src http://packages.dotdeb.org jessie all
Then run:
wget https://www.dotdeb.org/dotdeb.gpg
sudo apt-key add dotdeb.gpg
sudo apt-get update
Time to install PHP!
sudo apt-get install php-7.0
Installing support for certain packages is easy, just replace php5- with php7-!
Note: These instuctions do not work on ARM-based devices, such as the Raspberry Pi.

