Broken dependencies while installing GD Library for php5.6 on Linode server Debian 9

Question

I want to install GD Library for php5.6 on Linode Server Debian 9

I run apt-get install php5.6-gd

Output is:

php5.6-gd : Depends: libgd3 (>= 2.1.1) but it is not going to be installed

then I tried to install that package apt-get install libgd3 output is:

 libgd3 : Depends: libfontconfig1 (>= 2.11.94) but 2.11.0-6.7+b1 is to be installed
 Depends: libjpeg8 (>= 8c) but it is not installable

I tried to install the mentioned version by running command apt-get install libfontconfig1=2.11.94

Output is:

Version '2.11.94' for 'libfontconfig1' was not found

I checked the available versions of libfontconfig1 package by running :

apt-cache policy libfontconfig1

Output is :

libfontconfig1:

 Installed: 2.11.0-6.7+b1
 Candidate: 2.11.0-6.7+b1
 Version table:
2.11.0-6.7+b1 500
       500 http://mirrors.linode.com/debian stretch/main amd64 Packages
       100 /var/lib/dpkg/status

I didn’t find the (>= 2.11.94) version available.

Output of cat /etc/apt/sources.list

# deb http://mirrors.linode.com/debian/ stretch main

deb http://mirrors.linode.com/debian/ stretch main
deb-src http://mirrors.linode.com/debian/ stretch main

deb http://security.debian.org/debian-security stretch/updates main
deb-src http://security.debian.org/debian-security stretch/updates main

deb http://ftp.de.debian.org/debian stretch main

Output of cat /etc/apt/sources.list.d/*enter image description here

Answer 1

The problem is that http://ppa.launchpad.net/ondrej/php/ubuntu contains conflicting version of libgd3.

vagrant@localhost:~$ sudo apt-cache policy libgd3
libgd3:
  Installed: (none)
  Candidate: 2.2.5-3+ubuntu16.04.1+deb.sury.org+1
  Version table:
     2.2.5-3+ubuntu16.04.1+deb.sury.org+1 500
        500 http://ppa.launchpad.net/ondrej/php/ubuntu xenial/main amd64 Packages
     2.2.4-2+deb9u2 500
        500 http://deb.debian.org/debian stretch/main amd64 Packages
        500 http://security.debian.org/debian-security stretch/updates/main amd64 Packages

You need to install version from official repository like next:

vagrant@localhost:~$ sudo apt-get install libgd3=2.2.4-2+deb9u2

I hope this helps.