title: jquery closest('form') doesn't serialize
body: <p>I use it as a form for comment. There're many of this class on the page, so i have to choose the closest form but it doesn't work.</p>
  
  <pre><code>$(document).ready(function() {
  $(".comment_but").on('click',function(){
      var location2 = $(this).closest('div');
      var datastring = $(this).closest('form').serialize();
          $.ajax({
          type: "POST",
          url: "comment_save.php",
          data:  datastring,
          cache   : false,
          success: function(html){
  $('.comment_show',location2).html(html);}});});});
  </code></pre>
  
  <p>And my HTML</p>
  
  <pre><code>&lt;div class="comment_show"&gt;&lt;/div&gt;
  &lt;tr&gt;
          &lt;form onSubmit="return false;" name="comment_form" id="comment_form" style=" display:inline; "&gt;
              &lt;td align="right"&gt;&lt;textarea name="comment_box" cols="70" rows="2"&gt;&lt;/textarea&gt;&lt;/td&gt;
                          &lt;td&gt;
              &lt;input name="post_id" type="hidden" value="&lt;? echo($data['post_id']); ?&gt;" /&gt;
              &lt;input name="Send" class="comment_but" value="Comment!" type="submit" /&gt;&lt;/td&gt;
          &lt;/form&gt;
  &lt;/tr&gt;
  </code></pre>