Prestashop blank BO and FO because of Rijndael.php

Hello Prestashopper. Sometimes when you try to move your prestashop website from one hosting to a new hosting, or when you migrate your database to an existing website database, it may cause a Blank Back-Office and blank Front-Office !!! this is somehow confusing, but we can fix it as follows :

1- Open your site's file manager, and open config/config.inc.php
2- Search for @ini_set('display_errors', 'off') and change 'off' to 'on'.
3- Now refresh your Front Office, if you find the following error :
       Fatal error : Call to undefined function mcrypt_decrypt() in .................... Rijndael.php
4- Open your database using any database management system ( e.g phpmyadmin ).
5- Search for " PS_CIPHER_ALGORITHM " in " ps_configuration " table.
6- click on Edit, and change its value from 1 to 0.

7- Click Go.

and That's it.

Now your website will work perfectly.