Find out what time was last comment posted on a node I want to put a new icon next to node listed in a block if it was created/updated or commented on in last 1 day. I'm able to fetch all the nodes which were created/updated or commented on sorted in descending order of their time of creation/update or comment.

This is my code in template.php:

 function analytic_preprocess_views_view_fields(&amp;$vars) {
     $viewName = $vars['view']-&gt;name;
     $view1 = "view1";
     $view2 = "view2";
     $view3 = "view3";

    if (strcasecmp($viewName, $view1) == 0 ||
        strcasecmp($viewName, $view2) == 0 ||
        strcasecmp($viewName, $view3) == 0)
      {
           if (isset($vars['view']-&gt;name)) {
              $created = $vars['row']-&gt;node_created;
              $changed = $vars['row']-&gt;node_changed;

              $cexpire = $created + (1 * 24 * 60 * 60); //one day later
              $uexpire = $changed + (1 * 24 * 60 * 60); //one day later

              if (($cexpire &gt; time()) || ($uexpire &gt; time())) {
                    $vars['newicon'] = '&lt;img src="'. path_to_theme().'/images/new_icon.gif"&gt;';
              }
       }
    }
}


Problem is that when I commented on an older article which I created few months back, it was accurately displayed at the top of my block but 'NEW' icon didn't appear next to it and I saw this error on the page:

Notice: Undefined variable: newicon in include() (line 28 of /home/user/public_html/sites/all/themes/analytic/views-view-fields--viewname.tpl.php).

where I'm displaying/rendering this image. 

My understanding is that for the node which just has a new comment I don't have the time of update. How do I get that? Like I have node_created and node_changed.
node_created and node_changed refers only to node itself.

In views you should be able to add relationship " Comment: Last Comment".
Then, you'll have filter and field like "Comment: comment time". You can add this field as non-display one and then use it in templates for fields after it. Will be simpler and more reliable than preprocess functions.