[Mashiro]

@deanhills

Sorry for the late reply to your new message.

I'm afraid I'm no help in regards to this subject. The last time I touched phpBB was maybe about 10 years ago (+/- a few years). I guess since that time a lot has changed.

Generally said the PHP version could be an issue if the phpBB version doesn't support it but otherwise PHP won't be an issue for database related parts of phpBB. The phpBB requirements site that @fitkoh linked says phpBB 3.3 needs PHP 7.1 or higher. So you actually should be fine here.

The database version you have also seems to be fine as phpBB 3.3 requires MySQL 4.1.3 or MariaDB 5.1 or higher. You have 5.5.62. However as you noticed phpBB requires the mysqli driver while your own configuration still uses the mysql driver.

Basically what @fitkoh has linked to / already said in one or another way.


Edit: That said such major version upgrades over a long time are always a huge pain to deal with. Too many changes in code and database structure and etc.