Presta shop fatal error

[Kris10]

Hi I'm just wondering if any one might have some advice on how to to remove the following error:

Fatal error: Cannot redeclare pSQL() (previously declared in /home/partiesp/domains/*****.com.au/public_html/shop/config/alias.php:64) in /home/partiesp/domains/*******.com.au/public_html/shop/classes/Db.php on line 306

I'm new to presta shop and I'm just trying to learn the ropes with how to understand code  so I really need some help on this step by step as to how to remove this error.
The presta shop version I am using is 1.6

 

The error came up when i changed the Cache settings under preferences and then the website would no longer load.

If anyone has a simple solution that would be great.

 

Thanks :)