使用DOMDocument 和DOMXPath 你可以试试这个。

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

ob_start();  // run the_content() through the Output Buffer
the_content();
$html = ob_get_clean(); // Store the formatted HTML
$content = new DomDocument(); // Create a new DOMDocument Object to work with our HTML
$content->loadHTML( $html ); // Load the $html into the new object
$finder = new DomXPath( $content );  // Create a new DOMXPath object with our $content object that we will evaluate
$classname = \'ps_post_description\'; // The class we are looking for

$item_list = $finder->query("//*[contains(@class, \'$classname\')]"); // Evaluates our content and will return an object containing the number of items matching our query
?>

<li style = "text-align: center; float : left;">

  <a href="<?php the_permalink() ?>" title="<?php the_title(); ?>"><?php echo get_the_post_thumbnail($id); ?></a>

  <div class="title">
    <a href="<?php the_permalink() ?>" rel="bookmark" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a>
  </div>

  <div id = "result">`
    <?php 
    // echo the value of each item found
    // You might want to format or wrap your $value according to your specification if necessary
    for( $i = 0; $i < $item_list->length; $i++ ){
    $value = $item_list->item( $i )->nodeValue;

      echo $value;

      // if you want the text to be a link to the post, you could use this instead 
      // echo \'<a href="\' . get_the_permalink() . \'">\' . $value . \'</a>\';

    } ?>
  </div>

</li>

<?php endwhile; ?>

UPDATE

请注意，这两种解决方案（编辑之前和之后）都有效，因此错误/警告应该来自设置中的其他地方。