PHP5.6 is the latest version that is made available for Jessie; PHP7 is not available by default. Therefore we need to add the packages:
Add the repository
sudo touch /etc/apt/sources.list.d/mati75.list
edit the file /etc/apt/sources.list.d/mati75.list and add the following content:
deb http://repozytorium.mati75.eu/raspbian jessie-backports main contrib non-free
You'll need the GPG keys:
sudo gpg --keyserver pgpkeys.mit.edu --recv-key CCD91D6111A06851
sudo gpg --armor --export CCD91D6111A06851 | sudo apt-key add -
Now you can refresh your dependencies: sudo apt-get update
Install PHP7 dependencies for Nextcloud:
sudo apt install php7.1 php7.1-sqlite php7.1-zip php7.1-dom php7.1-xmlwriter php7.1-xmlreader php7.1-curl php7.1-gd php7.1-mb
Restart Apache: sudo service apache2 restart
By vinyll on Feb. 26, 2018