title: "Call to undefined function post_image_thumbnail()" Error
body: <p>I recently changed my WordPress theme. I have a custom page template that I am trying to move over to the new theme, but the custom page template is now throwing an error. </p>
  
  <blockquote>
    <p><strong>Fatal error:</strong> Call to undefined function <code>post_image_thumbnail()</code> in [link to custom page url] on line 55</p>
  </blockquote>
  
  <p>I thought it might be the child theme not supporting thumbnails, so I added this to the child theme's <code>functions.php</code>:</p>
  
  <p><code>add_theme_support( 'post-thumbnails' );</code></p>
  
  <p>But it didn't solve anything. </p>
  
  <p>Could someone help debug my code? Maybe I have a syntax error that I can't see? </p>
  
  <pre><code>&lt;h3&gt;&lt;?php echo get_cat_name(26);?&gt;&lt;/h3&gt;
  &lt;?php query_posts(array('category__and'=&gt;array(75,26),'meta_key'=&gt;'wpcf-sortname','orderby'=&gt;'meta_value','order'=&gt;ASC,'posts_per_page' =&gt; -1));if ( have_posts() ) while ( have_posts() ) : the_post(); ?&gt;&lt;div class="indentlist"&gt;&lt;?php post_image_thumbnail(); ?&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;&lt;a href="&lt;?php the_permalink() ?&gt;" class="participants"&gt;&lt;?php the_title(); ?&gt;&lt;/a&gt;&lt;/div&gt;&lt;?php endwhile; // end of the loop. ?&gt;
  </code></pre>
  
  <p>Thank you!</p>