gdk::pixmap_create_from_xpm() returns a array consisting of a GdkPixmap and a GdkBitmap mask that has been created from the specified .xpm file.

The GdkPixmap is the underlying structure that holds the image ready to be displayed in a GtkPixmap. In order to make that image appear on the screen, you will need to use one of the following constructs:

<?php

$gdkpixmap = gdk::pixmap_create_from_xpm($main_window->window, null, 
'test.xpm');
$image = &new GtkPixmap($gdkpixmap[0], $gdkpixmap[1]);

?>

<?php
list ($gdkpixmap, $mask) = 
gdk::pixmap_create_from_xpm($gdkwindow, $transparent_color, 'test.xpm');
$image = &new GtkPixmap($gdkpixmap, $mask);

?>

See the tutorial for more details and some examples.