Xdebug installation with php 5.6 and Ubuntu

First of all you have to install the xdebug package for php5.6

sudo apt-get install php-xdebug

Then you have to activate this one to be accessible with PhpStorm for example

Edit the file

sudo nano /etc/php/5.6/mods-available/xdebug.ini

and add the following lines

xdebug.remote_enable
xdebug.remote_connect_back
xdebug.idekey - "vagrant"

The php service needs to be restarted

sudo service php5.6-fpm restart

To control if all goes well

php -v
PHP 5.6.31-1-ubuntu14.04.1-deb.sury.org-1 (cli) 
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
    with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2016, by Zend Technologies
    with Xdebug v2.5.5, Copyright (c) 2002-2017, by Derick Rethans