An important hint: if you are using prebuilt PHP packages where PDO_OCI is not compiled in, you should download the original PHP sources for the PHP version your server is using.
These sources contain the PDO_OCI source in the ext/pdo_oci directory.
Change to that directory, build the module using
phpize
./configure
make
and then install the newly build module to your PHP extension directory and add it to your configuration.
For me this has worked on a Debian server with the sury.org modules (PHP 8.2).
