For MySQL, you'd need to set it via 'options' PDO array.
$dbConfig['options'] = [
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
PDO::ATTR_PERSISTENT => 1,
// Many web applications will benefit from making persistent connections to database servers. Persistent connections are not closed at the end of the script,
// but are cached and re-used when another script requests a connection using the same credentials.
// The persistent connection cache allows you to avoid the overhead of establishing a new connection every time a script needs to talk to a database, resulting in a faster web application.
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION