Blank page when accessing Joom!Fish

It's weird and scary - in a perfectly functioning Joomla site I installed one of my favourite components, Joom!Fish - remember, I'm the multilang guy Tongue out - and all I got was a blank screen. Obviously, something gone south... but what?

Firefox don't showed me anything usable, Chrome was the one to sow me the first clue: a 500 server error. Obviously Joom!Fish tried to access something forbidden by the server settings.

What to do next? Take a look to the error_log, obviously, and here I found the first clue:

PHP Fatal error:  Class 'DOMDocument' not found in /***/administrator/components/com_joomfish/models/cpanel.php on line 130

Humm, what a heck is this... Obviously, the next step was to search the Joom!Fish forums. I found a lot of bullshit, and another clue:

The problem is 99% related to your webserver configuration. check if PHP XML is enabled - if not contact your host!

What a heck... I just installed the latest CentOS with all the bells and whistles... who to ask? I asked myself already... Evil Uff... but let's make long story short, finally, in some other forum I found this:

This is the DOM manipulation classes in PHP (see http://www.php.net/manual/en/book.dom.php) and is enabled by default see http://www.php.net/manual/en/dom.installation.php

and then this:

In CentOS the php-xml package is not added by default. You need to install it manually. In the CLI (Command Line Interface) run the following command
yum install php-xml

This will install XML support and will solve the DOMDocument issue

Bingo! Mission accomplished.