What is the right way to use PDO directly in CodeIgniter 3?

Extend PDO in a library. Load or autoload the library and make your connection in the constructor using custom configuration. You can see examples of this all over the internet. Since you're a newbie, this is a good way to learn how to use libraries with CodeIgniter. The problem would be that some other CodeIgniter libraries (or at least 1) depend on the CodeIgniter database connection. Sessions do if you use the database sessions.

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