Trying to pass like second argument PDO::FETCH_ASSOC it still work.
So passing FETCH TYPE like argument seems work.
This save you from something like:
<?php
$result = $stmt->setFetchMode(PDO::FETCH_NUM);
?>
Example:
<?php
$res = $db->query('SELECT * FROM `mytable` WHERE true', PDO::FETCH_ASSOC);
?>