Description:
------------
PDO doesn't throw any exception (at least with Oracle) in some cases but I can see the error with $db->errorInfo(). I notice this happens when I bind some unexistent variables to the query. I know it is wrong (bind unexistent variables) but in my opinion PDO must throw an exception (because $db->errorInfo() knows the error)

Reproduce code:
---------------
// create table TBLDUMMY (FIELD1 VARCHAR2(2), FIELD2 VARCHAR2(2))
$db = new PDO(
    $dsn, // my DB dsn
    $user, // database username
    $password); // database password
try {
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $sql = "select FIELD1, FIELD2 FROM TBLDUMMY";
    //$sqlOK = "select FIELD1, FIELD2 FROM TBLDUMMY WHERE FIELD1=:F1";
    $stmt = $db->prepare($sql);
    $stmt->execute(array('F1' => '1'));
    $result = $stmt->fetchAll();
    echo "<pre>";
    print_r($db->errorInfo());
    echo "</pre>";

} catch (Exception $e) {
    echo "Exception:" . $e->getMessage();
}

Expected result:
----------------
Exception OCIBindByName: ORA-01036: n?mero/nombre de variable no v?lido


Actual result:
--------------
Array
(
    [0] => HY000
    [1] => 1036
    [2] => OCIBindByName: ORA-01036: n?mero/nombre de variable no v?lido
 (/usr/local/PDO_OCI-1.0/oci_statement.c:287)
)