Example issue:
Message: mysqli::real_connect(): Headers and client library minor version mismatch. Headers:50550 Library:100029
Sounds like server issue. PHP and MySQL versions not compatible.
Try this solution: https://stackoverflow.com/questions/10759334/headers-and-client-library-minor-version-mismatch
If this is localhost try with:
For localhost, you can for example (Windows guide):
Install portable XAMPP Version 5.6.3
Create folder in (depends where you install xampp): C:\xampp\htdocs\mywebsite