How to setup xdebug for remote debugging

xdebug (remote)

# install xdebug extension
apt install php-xdebug

# config xdebug
/etc/php/7.2/<fpm> or <apache2>/conf.d/20-xdebug.ini
  zend_extension=xdebug.so
  xdebug.remote_enable = 1
  xdebug.remote_connect_back = 0
  xdebug.remote_host = localhost
  xdebug.remote_port = 9001
  xdebug.max_nesting_level = 512
  
# open ssh session with port forwarding
ssh -R 9000:localhost:9000 <user>@<host>

# setup mapping in phpstorm
Settings => Languages and Frameworks => PHP => Servers