Site Map and Page-o-mation

I need help with a site map I am making using PHP. The site map is of an
online photo gallery.

In the code below I am trying to determine the <lastmod> value for the
photo theme (category) thumbnail image pages.  Each of the photo theme
(category) pages may display up to 18 thumbnail images and then the next
web page is made.  I use page-o-mation to offer the subsequent pages for
photos that are of similar content.

The code below is what I have come up with so far.  Where I am stuck is
determining the most recent photo_gallery_index.last_update value for
the up to 18 photos thumbnails which are being displayed.  

I am wondering if I should be doing this WHILE loop, to scan the up to
18 images.  

So far my results only incorporate the first image being displayed. 

Any suggestions?

Ron



$page_link=1;
$ii=0;

$last_update = "0000-00-00";

while ($ii < $number_of_images) { 

$current_photo_last_update = mysql_result($image_result,
$ii,"photo_gallery_index.last_update");
if ( $current_photo_last_update > $last_update ) { $last_update =
$current_photo_last_update; }

$site_map .= "  <url>\r\n";
$site_map .= "
<loc>http://www.rons-home.net/photo-gallery-category/" .
stripslashes($photo_gallery_category) . "/" . $page_link . "/</loc>\r
\n";
$site_map .= "      <lastmod>" . $last_update . "</lastmod>\r\n";
$site_map .= "      <changefreq>weekly</changefreq>\r\n";
$site_map .= "      <priority>1</priority>\r\n";
$site_map .= "   </url>\r\n";

++$page_link;
$ii=$ii+18;
}