class DB_CONNECT {

    public $con = null;

    function __construct($host) {
        $this->connect($host);
    }

    function __destruct() {
        $this->close();
    }

    function connect($host) {

        $this->con = mysqli_connect($host, DB_USER, DB_PASSWORD, DB_DATABASE);
        $this->con->set_charset("utf8");
    }

    function close() {
    if($this->con)
           mysqli_close($this->con);
    }
}


$db = new DB_CONNECT('database-server-001');

$db->close();

$db = new DB_CONNECT("database-server-002");

$query = "SELECT * from his_track_recods";

$getHistResult = mysqli_query($db->con, $query);