title: Wordpress change post thumbnail attributes
body: <p>I'm trying to change the post thumbnail's attributes to support <a href="http://www.appelsiini.net/projects/lazyload" rel="nofollow">Lazy Load</a>. This requires me to add a class of <code>lazy</code>, change the source to a placeholder image, and place the image source to into a <code>data-original</code> attribute.</p>
  
  <p>I've done research and have referenced the <a href="http://codex.wordpress.org/Function_Reference/the_post_thumbnail" rel="nofollow">documentation</a>, but am still running into issues.</p>
  
  <p>Here's the code I'm trying to use:</p>
  
  <pre><code>&lt;?php
      $tempimg = get_bloginfo('template_url') . "/img/grey.gif";
      $default_attr = array(
          'src' =&gt; $tempimg,
          'data-original' =&gt; $src,
          'class' =&gt; "lazy attachment-$size",
      );
      the_post_thumbnail('project-thumbnail', $default_attr);
  ?&gt;
  </code></pre>
  
  <p>You'd think it would work, but once I use those attributes, the <code>$src</code> and <code>$size</code> variables don't work. They're just blank. Is there something I am missing?</p>
  
  <p>Thanks in advanced.</p>