这就是我加载后期缩略图图像的方式？

如果没有图像，我想显示默认图像怎么办？

我怎样才能证明这一点。

下面是我用来显示缩略图的代码。

        $html .= \'<div class="post event" id="post-\'.$post->ID.\'">

                    <a href="\'.get_permalink($post->ID).\'"> \'.get_the_post_thumbnail().\' </a>

                    <div class="content">
                        <span class="title">
                            <a title="\'.$post->post_title.\'" href="\'.get_permalink($post->ID).\'">\'.$post->post_title.\'</a>
                        </span>                                             
                        <div class="addl-123">\';                            

                    $terms = wp_get_post_terms($post->ID, \'sublocation\');
                    if($terms)
                    {
                        $out = array();
                        foreach ($terms as $term)
                        {
                            $out[] = \'<a class="\' .$term->slug .\'" href="\' .get_term_link( $term->slug, \'sublocation\') .\'">\' .$term->name .\'</a>\';
                        }
                        //echo join( \', \', $out);
                        $html .= join( \', \', $out);
                    }

                    if($is_parent != 0)
   {
    $address = get_post_meta($is_parent,\'address\',true);
         }
   else
   {
    $address = get_post_meta($post->ID,\'address\',true);
         }
         if(!$address){ $address=\'-\'; }
   if($address && $address!="-"){$html .= "<b>".$address."</b>";}

    $html .= \'<p>Timinigs: \'.get_post_meta($post->ID, \'cstimings\', true). \' </p>\';

        $html .= \'</div>

在代码的第2行，我能够显示具有特色图像的帖子的缩略图。但其他帖子没有特色图片。所以，对于这样的帖子，我想显示默认图像。

我该怎么做？

<?php $featured_image = ( \'\' != get_the_post_thumbnail() ? get_the_post_thumbnail() : get_template_directory_uri() . \'/images/img_not_available.png\' ); ?>

<a href="<?php the_permalink(); ?>"><?php echo $featured_image; ?></a>

    function wpforce_featured() {
      global $post;
      $already_has_thumb = has_post_thumbnail($post->ID);
          if (!$already_has_thumb)  {
          $attached_image = get_children( "post_parent=$post->ID&post_type=attachment&post_mime_type=image&numberposts=1" );
                      if ($attached_image) {
                            foreach ($attached_image as $attachment_id => $attachment) {
                            set_post_thumbnail($post->ID, $attachment_id);
                            }
                       } else {
                            set_post_thumbnail($post->ID, \'414\');
                       }
                    }
  }  //end function
add_action(\'the_post\', \'wpforce_featured\');
add_action(\'save_post\', \'wpforce_featured\');
add_action(\'draft_to_publish\', \'wpforce_featured\');
add_action(\'new_to_publish\', \'wpforce_featured\');
add_action(\'pending_to_publish\', \'wpforce_featured\');
add_action(\'future_to_publish\', \'wpforce_featured\');

<?php if ( has_post_thumbnail()):
    the_post_thumbnail();   
else: ?>
<!-- Do default stuff here -->
<?php endif; ?>