some advance help needed for : IF ELSE

Hi,
i try to do a code who print a default img (no-img.jpg) if the required one dont poste by user, and now i dont know wher i make a mistake, the code dont print the default img:

<?php if (have_posts()) : while (have_posts()) : the_post(); ?>

<?php // if there's a img in my custom field
if($value !== '') { ?>
<img src="<?php $values = get_post_custom_values("my-img"); echo $values[0]; ?>">
<?php } // end if statement
// if there's no img
else { ?>
<img src="<?php bloginfo('stylesheet_directory'); ?>/images/no-img.jpg" />
<?php } ?>

<?php endwhile; else: ?>
<?php endif; ?>

thanks for any idea and help.