Remote Linux server PHP debugging using PhpStorm Xdebug with its port forwarded through SSH tunnel

If your client's site setup is complicated and you don't have time to replicate it in your local machine, your choice is to debug it directly. This article will show steps on how to debug a website's PHP codes remotely in a server with firewall specifically hosted in Linode server running Centos 7 64-bit Linux distribution, PHP-FPM (FastCGI Process Manager) and PHP 7.0 (the server is running multiple PHP versions).