19 hours ago, rcitaliano said:I've found, looking at prestashop's code that it uses a different approach, using some PDO class, I suppose it is an implementation of some sort of interface that then uses mysql... is this so?
Yes. The fact that mysqli calls works but Prestashop fails indicates that you need the pdo_mysql extension added to your php config.
EDIT: Also make sure that the values returned by those environment variables match what you put in the Prestashop config (or use the environment variables themselves).