//Creating a GtkHButtonBox
     $hbbox = new GtkHButtonBox();
     //Selecting a layout for the button box. Try other
     //GtkButtonBoxStyle options to see the diference  
     $hbbox->set_layout(Gtk::BUTTONBOX_SPREAD);
     //Setting the spacing
     $hbbox->set_spacing(25);
 
     //Creating buttons to add
     $button1 = new GtkButton('Button 1');
     $button2 = new GtkButton('Button 2');
 
     //Adding the buttons to the GtkHButtonBox
     $hbbox->add($button1);
     $hbbox->add($button2);