title: Wordpress - how to insert code into the head?
body: <p>I'm having a Like button on my Wordpress site. I'd like to use the og:image meta-tag from facebook to display the proper image when somebody likes it. 
  I need to add that tag in the head of the page.
  So far I have this in single.php:</p>
  
  <pre><code>function fb_image_meta($image) {
      return '&lt;meta property="og:image" content="$image" /&gt;';
  }
  
  add_action('wp_head', 'fb_image_meta', 10, $image_thumbnail); 
  </code></pre>
  
  <p>When I look at the source of an article, The meta tag doesn't show up.</p>
  
  <p>What am I doing wrong?</p>