vlill

Ok, I solved it. Relevanssi Premium doesn’t work with PHP 5.2.17, works fine after I upgraded to PHP 5.4.

More info:
Wordpress version: 4.0.12
PHP 5.2.17

Other plugins installed:
Sucuri Security
Advanced Custom Fields
Advanced Custom Fields: Date and Time Picker
Advanced Custom Fields: Options Page
Simple Follow Me Social Buttons Widget
Yet Another Related Posts Plugin

Thank u! I did and I still get the same errors.