EE 2.9.11 to 3.5.17 update - PDO driver error

I updated php 5.x to 7.4.x on my Windows IIS server as a test to see which web apps broke. I had to change the EE driver from mysql to mysqli but otherwise v2 is connecting to the database but is just throwing errors, which I expect.

I want to migrate EE 2 to 5 to see how much development work is required.

I’m trying to test an upgrade from EE 2 to EE 5. The first part of this is to go from 2 to 3.

I followed the instructions and copied over the database.php and config.php file but the updater is giving a database connection error. I then ran the wizard and it gave this error:

> “Fatal error: Uncaught PDOException: could not find driver”

I then went into the server’s php.ini file and enabled this line to fix that PDO error:

extension=php_pdo_mysql.dll

That fixed the wizard pdo error, and an update to v.3 from v.2 then worked.

I don’t see this PDO driver listed as a requirement in the v3 documentation.

Why would v2 work with mysqli and php 7 but v3 doesn’t?

Thank you for any clarity you can provide…