php - sqlsrv_query（）期望参数1是资源，给定布尔值

I was trying to run a simple query through sqlsrv_query. I have a class which connect to the database:

class ConexionDB
{

    private $server = SERVIDOR;
    private $user = USUARIO;
    private $passw = PASSW;
    private $db_name = DB_NAME;

    private $conn;
    private $error;
    private $stmt;

    function __construct()
    {
        try {

            $this->conn = sqlsrv_connect($this->server, 
                            array(
                                "Database" => $this->db_name,
                                "UID" => $this->user,
                                "PWD" => $this->passw
                            )
                    );

        } catch (Exception $e) {
            throw $e;
        }
    }

    function query($query)
    {
        $this->stmt = sqlsrv_query($this->conn, $query);
    }

}

And I have a DAO class which make the query like this:

$database = new ConexionDB();

$sql = " SELECT *
            FROM SistemaWeb.dbo.Empresa  ";

$database->query($sql);

But the result gives me this error:

sqlsrv_query() expects parameter 1 to be resource, boolean given

What could be wrong? Thanks for replies.

Edit: Here is the result of the query through SQL Management:

Hei friend try to change the fields above From

private $server = SERVIDOR;
private $user = USUARIO;
private $passw = PASSW;
private $db_name = DB_NAME;

To

private $server = "SERVIDOR";
private $user = "USUARIO";
private $passw = "PASSW";
private $db_name = "DB_NAME";

This should avoid the connection keeps failing.