Exclude empty image field

[Sensas]

Sorry for this noob  question, but I am calling images from a database and I don't want to show the empty images.

Example webpage here

As you can see, there are 3 empty image fields left. How do I exclude empty fields in the code below

Code: [Select]

             <a href="<?php echo $listing_photo1; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo1; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo2; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo2; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo3; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo3; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo4; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo4; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo5; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo5; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo6; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo6; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo7; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo7; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo8; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo8; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo9; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo9; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo10; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo10; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo11; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo11; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo12; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo12; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo13; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo13; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo14; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo14; ?>" width="90" height="66" /></a>
             <a href="<?php echo $listing_photo15; ?>" rel="lightbox[roadtrip]"><img src="<?php echo $listing_photo15; ?>" width="90" height="66" /></a>
Thanks a lot!