Personal COMBO BOX problem with keybord keys in popup wondow

I'm trying to build i new combo with 2 columns in list.

So I've used a gtkentry in a main window witha button to open a list
the list is into a popup window without decorations

The list is opened with button and then I would choose the row with
cursor keys but I'm not able to use the keyboard

Anyone can help me?

<?php
$window = &new GtkWindow();
$window->connect_simple('destroy', array( 'Gtk', 'main_quit'));
$window->set_size_request(-1,-1);

$window->add($vbox = new GtkVBox());


// the initial selection
$list = array('item 1', 'item 2', 'item 3', 'item 4');

$vbox->pack_start($hbox=new GtkHBox(), 0, 0);
$hbox->pack_start($label= new GtkLabel('Select: '), 0, 0);
$hbox->pack_start($entry =  new GtkEntry(), 0, 0);
$hbox->pack_start($button = new GtkButton('V'), 0, 0);

$button->set_size_request(18,18);
$button->connect('clicked', "on_button");

//========================================================================
function on_button($button) { // process button click
global $window, $entry;

  // == ENTRY POSITION
  $win_pos=$window->get_position();
  $x_field_pos=$entry->allocation->x;
  $y_field_pos=$entry->allocation->y;
  $x_shift=4;
  $y_shift=23+$entry->allocation->height;
 
  $x_win=$win_pos[0]+$x_field_pos+$x_shift;
  $y_win=$win_pos[1]+$y_field_pos+$y_shift;
 
  //==============================================
  // CREO LA FINESTRA
  $sub_list = &new GtkWindow(Gtk::WINDOW_POPUP);    
 
  $sub_list ->set_size_request(400,250);
  $sub_list ->set_uposition($x_win,$y_win);
  $sub_list ->set_modal(true);
  $sub_list ->set_transient_for($window);
  //=========================================
 
  $sub_list->add($vbox = new GtkVBox());
 
  // Set up a scroll window
  $scrolled_win = new GtkScrolledWindow();
  $scrolled_win->set_policy( Gtk::POLICY_AUTOMATIC, Gtk::POLICY_AUTOMATIC);
  $vbox->pack_start($scrolled_win);
// ==================================================  
// INSERISCO IL GTKTREEVIEW NEL SCROLLED WINDOW
$data=array(
      array("01","Ferro"),
      array("02","Acciaio"),
      array("03","Tungsteno"),
      array("042","Rame"),
      array("044","Piombo"),
      array("05","Alluminio"),
      array("06","Carbonio"),
      array("07","Uranio"),
      array("08","Cobalto"),
      array("07","Plutonio"),
      array("08","Ottone"),
      array("09","Zama"),
      array("10","Molibdeno"),
      array("11","Bronzo"),
      array("12","Oro"),
      array("13","Argento"),
      array("14","Platino"),
      array("15","Berillio")
      );
     
  display_table($scrolled_win, $data);

 
// =================================================  

 
  $vbox->pack_start($button = new GtkButton('Chiudi'), 0, 0);
  $button->connect('clicked', "on_destroy",$sub_list);
 
  $sub_list ->show_all();
     
}



function display_table($scrolled_win, $data) {
    // Creates the list store
    $model = new GtkListStore(Gtk::TYPE_STRING, Gtk::TYPE_STRING); // note 2
    $field_header = array('Row #', 'Description'); // note 3

    // Creates the view to display the list store
    $view = new GtkTreeView($model); // note 4
    $scrolled_win->add($view); // note 5

    // Creates columns
    for ($col=0; $col<count($field_header); ++$col) {
        $cell_renderer = new GtkCellRendererText();
        $column = new GtkTreeViewColumn($field_header[$col], $cell_renderer, 'text', $col);
        $view->append_column($column);
    }

    // pupulates the data
    for ($row=0; $row<count($data); ++$row) {
        $values = array();
        for ($col=0; $col<count($data[$row]); ++$col) {
            $values[] = $data[$row][$col];
        }
        $model->append($values); // note 6
    }
   
   
}





function on_destroy($button,$obj) {
  $obj->destroy();
}

$window->show_all();
Gtk::main();
?>