onKeyDown() and keydown(i) in GUIControls

[AlexanderK]

I'm modifying my inventory to work with the keyboard, but I'm running into some problems
Why doesn't this work?

PHP Code:

function onMenuKeyDown() {
   player.chat="MenuKeyDown";
   if (keydown(8)) {
     player.chat="TAB";
     Inventory_Categories.forceonaction();
  }
} 


The player only chats "MenuKeyDown".

So I'm doing this instead,which works, but can I even use keycodes? Aren't they platform specific?

PHP Code:

function onMenuKeyDown(gui,keycode) {
   player.chat="MenuKeyDown";
   if (keycode==9) {
     player.chat="TAB";
     Inventory_Categories.forceonaction();
  }
}