What I have done

I have set up a LAMP webserver using these commands:

sudo apt-get install apache2
sudo apt-get install mysql-server
sudo apt-get install php5 libapache2-mod-php5
sudo /etc/init.d/apache2 restart

Then I installed phpmyadmin with:

sudo apt-get install phpmyadmin

The problem

The problem is that when I go to http://localhost/phpmyadmin/, I get this:

phpMyAdmin - Error
The json extension is missing. Please check your PHP configuration.

What I've tried

I've tried:

• https://superuser.com/questions/639945/how-to-fix-the-phpmyadmin-error-json-extension-is-missing
• https://stackoverflow.com/questions/27818040/phpmyadmin-error-the-json-extension-is-missing
• https://www.youtube.com/watch?v=WoLKOBmikXo

System info

• Clean install of Ubuntu 14.04 x64