Coneccion a DB con objetos (ayuda)

[Italico76]

He cambiado una parte.... pero ahora me da error en mysql_query

class DB_SQL{
private $conexion;
private $total_consultas;

/* public: connection parameters */

public $host = "localhost";
public $database = "betadir";
public $user = "betadir";
public $password = "xxxxxxxx";

public function DB_SQL() {
// constructor
if(!isset($this->conexion) && isset($host) && isset($user) && isset($password) ){
//echo $host." ".$database." ".$user." ".$password;
$this->conexion = (mysql_connect($this->$host,$this->$user,$this->$password)) or die(mysql_error());
mysql_select_db($database,$this->conexion) or die(mysql_error());
}
}

(...)

El error ahora es Warning: mysql_query(): supplied argument is not a valid MySQL-Link resource in C:\xampp\htdocs\class.mysql.inc on line 31

PD: ahora estoy probando llamar directamente a la subclase DB_SQL