DevOps, CI/CD and Automation

I skimmed through the 'oracle underground manual' and it said the oci method is prefered. but i was wondering doesn't PDO use some sort of OCI libraries/functions anyway, aka maybe even the same ones?
aka if you use PDO for oracle, does it internally though abstraction use php's oci_connect() to connect to your oracle database?

so basically im also asking... when u enable pdo and its oci .dll...
extension=php_pdo.dll
extension=php_pdo_mysql.dll
extension=php_pdo_oci.dll
Is the php_pdo_oci.dll just an interface to interact with php's oci functions. Just thought I'd ask cause it seems like they are separate, but i read somewhere pdo uses oci libraries not sure exactly what that means since you have options of oci or pdo and that statement sounds like the technologies merge/overlap a little (at least from pdo's side).