In PHP, How do I set default PDO Fetch Class?

Question

Using PDO::setAttribute, how do I provide the class name when setting PDO::ATTR_DEFAULT_FETCH_MODE to PDO::FETCH_CLASS.

This is the code I am using.. I would like to set it so all of my rows are returned as an instance of DB_Row:

class DB_Row extends ArrayObject {}

$db = new PDO('mysql:dbname=example;host=localhost', 'user', 'pass');
$db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS);

$stmt = $db->query("SELECT * FROM `table` WHERE `id` = 1;");

$row = $stmt->fetch(); // I want a DB_Row by default!

The code above results in a PDOException since the DB_Row class name was not assigned.

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General    error: No fetch class specified

How would I go about this?

Thanks in advance..

SOLUTION: I used fireeyedboy's answer. It worked the best for my situation as I was already extending PDOStatement for logging purposes...

class DB extends PDO {
    public function __construct($host = null, $user = null, $pass = null, $db = null) {
        try {
            parent::__construct('mysql:dbname=' . $name .';host=' . $host, $user, $pass);
            $this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS);
            $this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('DB_Query', array('DB_Row')));
        } catch (PDOException $e) {
            die('Database Error');
        }
    }
}

class DB_Query extends PDOStatement {
    private $class;
    protected function __construct ($class = 'DB_Row') {
        $this->class = $class;
        $this->setFetchMode(PDO::FETCH_CLASS, $this->class);
    }
}

class DB_Row extends ArrayObject {
    public function __set($name, $val) {
        $this[$name] = $val;
    }
    public function __get($name) {
        return $this[$name];
    }
}

Answer 1

I think it should return a stdclass instance so this would be a bug - but would have to look it up in the code to verify. will do if there is no accepted answer till then.

What will work is to use PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE and then provide a class name as first column. While this is a hack:

$db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE);

$stmt = $db->query("SELECT 'classname', * FROM `table` WHERE `id` = 1;");

EDIT: As promised here the code. The relevant code is here http://lxr.php.net/xref/PHP_5_4/ext/pdo/pdo_stmt.c#940 So setting the for using fetch() is only possible with FETCH_CLASSTYPE. The alternative is using PDOStatement::fetchObject()