Database connection failed: No such file or directory

Hi there!
I’m getting in contact in relation to a problem we are experiencing with OJS v 3.1.1-4 and PHP v7.0. I’m wondering if you could help me out with an error:

Database connection failed: No such file or directory

Our configuration is Driver in config.inc.php is mysqli.
Could you let me know if the error message has anything to do with how we set up Driver in config.inc.php?
Many thanks!