To display an image, you need to render it onto a GdkDrawable, such as GdkWindow of a drawing area or to a GdkPixmap which is then displayed in the usual ways.

<?php
  GdkPixbuf
::render_to_drawable(GdkDrawable  $drawable,
                                
GdkGC        $gc,
                                
int          $src_x,
                                
int          $src_y,
                                
int          $dest_x,
                                
int          $dest_y,
                                
int          $width,
                                
int          $height,
                                
GdkRgbDither $dither,
                                
int          $x_dither,
                                
int          $y_dither)
?>
$drawable
the drawable to render the image to

$gc
GC specifying rendering parameters

$src_x, $src_y
start coordinates within the source image

$dest_x, $dest_y
destination coordinates within the drawable

$widget, $height
the dimensions of the rectangle to render

$dither
dithering type - only makes sense on 8-bit or 16-bit displays. Use GDK_RGB_DITHER_NORMAL for most of cases.

$x_dither, $y_dither
dithering offset - useful only on 8/16-bit displays when scrolling or re-rendering sub-regions of the image