PDO to Oracle db and secure external password store aka wallet for authentication

Hi there, I am wondering how it would be possible to use authentication using a secure external password store aka wallet with PDO OCI. See Oracle external authentication and OCI_CRED_EXT in the underground php oracle manual. and https://docs.oracle.com/en/database/oracle/oracle-database/19/dbseg/configuring-authentication.html#GUID-803496D2-19C7-4F02-94EC-C13EDD8FB17B (jump to chapter 3.2.9) Following works fine with oci8: $conn = oci_connect('/', '', $db, 'UTF8',OCI_CRED_EXT); note the OCI_CRED_EXT! But how can pass that option to a PDO OCI connection? Following might be close, but does not work: $opt = [ PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION, PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_NUM, 'session_mode' => OCI_CRED_EXT, ]; try{ $conn = new PDO("oci:dbname=".$db.';charset=UTF8', "/","", $opt); } catch(PDOException $e){ echo ($e->getMessage()); } Is it possible at all? Thanks in Advance Mathias Zarick