class SQL {
        public static function Connect($db) {
            $host = "your host";
            $user = "my username";
            $pass = "my pass";

            $conn = mysql_connect($host, $user, $pass, $db);
            return $conn;
        }
    }

    //usage?

    $sql = SQL::Connect("users"); //connected to the database users

    $sql->query("INSERT INTO users .... .. .. . .");
    $sql->close();