Installing and enabling Xdebug in Debian 9

Install Xdebug:

sudo apt install php-xdebug;

Add the following to /etc/php/7.0/mods-available/xdebug.ini:

xdebug.profiler_enable_trigger = 1 xdebug.profiler_enable = 0 xdebug.remote_enable = 1 xdebug.profiler_output_dir = "/tmp"

Restart Apache: sudo service apache2 restart;

Now, all you have to do is create a debugging configuration in PhpStorm (hopefully :-)), and use Xdebug helper for extra convenience.