PHP odbc_connect（）不工作，没有错误消息

Question

Im trying to user odbc_connect() to connect to a SQL Server 2000 database.

ini_set('display_errors', '1');
error_reporting(E_ALL);

    $conn = odbc_connect('odbc:Driver={SQL Server};Server=ServerName;Database=dbName', 'sa', 'pass');
    var_dump($conn);

I only get this:

Warning: odbc_connect(): in C:\xampp\htdocs\manantiales\prueba.php on line 5
bool(false)

That's it .... I haven't the faintest idea of what's going on ... could it be that some file is missing?

I checked in the php.ini file and it says that odbc support is built-in and no dll is needed ......