title: How can I retrieve all comments on a Facebook post using the php SDK?
body: <p>I'm building an app which allows users to post articles to their facebook wall.  When an article is posted, I retrieve the post id and store that in the database along with the rest of the article details.  Now I want to be able to show the comments made on that post when someone views the article in my site; I would also like to allow users to add comments to the post from my site.</p>
  
  <p>I know that the user is always logged into Facebook when they are viewing the article, as the system checks for that earlier on.</p>
  
  <p>I've been using the PHP SDK, and thought all I had to do was something like:</p>
  
  <pre><code>$post_comments = $facebook-&gt;api('/' . $post_id . '/comments');
  </code></pre>
  
  <p>However, when I do this, I get the following error:</p>
  
  <p>Fatal error: Uncaught GraphMethodException: Unsupported get request. thrown in /APP_PATH/facebook/src/facebook.php on line 560</p>
  
  <p>I really don't have much of a clue what I'm doing here, to be honest, as I'm very new to the Facebook Graph API, and I can't seem to find a lot of documentation on it.</p>
  
  <p>Can anyone tell me what I should be doing here, or point me to some documentation I could read about it?</p>
  
  <p>Thanks!</p>