In a majority of cases, it is not advisable to set the size or position of the widget explicitly. The reason is that this disregards any external constraints that might be imposed on a widget, such as user's preference for the font size, resizing of the dialog box, the length of the button label in another language. It is best to let the containers choose the sizing and placement of their children.

That said, a few widgets should have their size and position set manually. This includes GtkWindow, GtkCTree, GtkCList, and a couple of others. To accomplish this, use these methods:

<?php
  $window
->set_usize($width$height);
  
$window->set_uposition($x$y);
?>