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Sorry to hear you’re facing problems 
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example
Or for longer, use three backticks above and below the code snippet:
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Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 12.0.2): 13.0.2
Operating system and version (eg, Ubuntu 17.04): Raspbian 8 (Jessie)
Apache or nginx version (eg, Apache 2.4.25): nginx/1.6.2
PHP version (eg, 7.1): 5.6.30
The issue you are facing: I cannot install PHP 7 on my server. I added deb http://packages.dotdeb.org jessie all and deb-src http://packages.dotdeb.org jessie all to /etc/apt/sources.list.
Then I fetched and installed GPG key and then apt-get update. Then I tried to install. Output beneath.
Is this the first time you’ve seen this error? (Y/N): Y
The output of your console log in:
root@nextcloud:/tmp# sudo apt-get install libapache2-mod-php7.0 php7.0-apcu php7.0-apcu-bc php7.0-cli php7.0-common php7.0-curl php7.0-gd php7.0-igbinary php7.0-imagick php7.0-imap php7.0-intl php7.0-json php7.0-mbstring php7.0-mcrypt php7.0-mysql php7.0-opcache php7.0-phpdbg php7.0-readline php7.0-redis php7.0-sqlite3 php7.0-xml php7.0-zip
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package libapache2-mod-php7.0
E: Couldn't find any package by regex 'libapache2-mod-php7.0'
E: Unable to locate package php7.0-apcu
E: Couldn't find any package by regex 'php7.0-apcu'
E: Unable to locate package php7.0-apcu-bc
E: Couldn't find any package by regex 'php7.0-apcu-bc'
E: Unable to locate package php7.0-cli
E: Couldn't find any package by regex 'php7.0-cli'
E: Unable to locate package php7.0-common
E: Couldn't find any package by regex 'php7.0-common'
E: Unable to locate package php7.0-curl
E: Couldn't find any package by regex 'php7.0-curl'
E: Unable to locate package php7.0-gd
E: Couldn't find any package by regex 'php7.0-gd'
E: Unable to locate package php7.0-igbinary
E: Couldn't find any package by regex 'php7.0-igbinary'
E: Unable to locate package php7.0-imagick
E: Couldn't find any package by regex 'php7.0-imagick'
E: Unable to locate package php7.0-imap
E: Couldn't find any package by regex 'php7.0-imap'
E: Unable to locate package php7.0-intl
E: Couldn't find any package by regex 'php7.0-intl'
E: Unable to locate package php7.0-json
E: Couldn't find any package by regex 'php7.0-json'
E: Unable to locate package php7.0-mbstring
E: Couldn't find any package by regex 'php7.0-mbstring'
E: Unable to locate package php7.0-mcrypt
E: Couldn't find any package by regex 'php7.0-mcrypt'
E: Unable to locate package php7.0-mysql
E: Couldn't find any package by regex 'php7.0-mysql'
E: Unable to locate package php7.0-opcache
E: Couldn't find any package by regex 'php7.0-opcache'
E: Unable to locate package php7.0-phpdbg
E: Couldn't find any package by regex 'php7.0-phpdbg'
E: Unable to locate package php7.0-readline
E: Couldn't find any package by regex 'php7.0-readline'
E: Unable to locate package php7.0-redis
E: Couldn't find any package by regex 'php7.0-redis'
E: Unable to locate package php7.0-sqlite3
E: Couldn't find any package by regex 'php7.0-sqlite3'
E: Unable to locate package php7.0-xml
E: Couldn't find any package by regex 'php7.0-xml'
E: Unable to locate package php7.0-zip
E: Couldn't find any package by regex 'php7.0-zip'
root@nextcloud:/tmp#
What am I doing wrong. Found a lot of similar manuals, but nothing did work so far. Your assistance is highly appreciated.
Kind regards
//neph
But I had a lot of work with this what I tried to avoid. Anyhow, now I have a 15er running on Debian 9 with PHP 7.0.