On the single post page for our posts, we wanted to display the excerpt only if one had been entered. Since the built-in WordPress function to get the excerpt for a post will automatically generate one for you, we couldn’t just put the function in our post loop like what was done below.

<?php if ( have_posts() ) while ( have_posts() ) : the_post(); ?>
	<div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
		<h1 class="entry-title"><?php the_title(); ?></h1>
		<div class="entry-content">
			<?php the_excerpt(); ?>
			<?php the_content(); ?>
		</div><!-- .entry-content -->
	</div><!-- #post -->
<?php endwhile; // end of the loop. ?>

Doing this causes the intro of the post to show twice, once from the auto-generated excerpt and once in the post content. To fix this, we added a quick check to the post loop. Simply replacing the_excerpt function in the post loop with this little piece of code removed the double intro.

<?php 
	if( !empty($post->post_excerpt) ) {
		//We have a excerpt so print it
		the_excerpt();
	} 
?>