Add body class to both Node add and Node Edit Page I want to add a Body class to my Node Add pages and my Node Edit Pages. 

How can I do this?

I know that I need use the following in template.php to add a class to Node Edit:

function MYTHEME_preprocess_html(&amp;$variables) {
     if (arg(0)=='node' &amp;&amp; arg(2)=='edit') {
      $variables['classes_array'][] = 'node-edit-page';
    }
}


But how can I modify the code to work with node add?

Note: Node Add is when you create a node (e.g. yousite.com/node/add/page). 

Node Edit is when you edit an existing page  (e.g. yousite.com/node/1/edit)
Did you try :

function MYTHEME_preprocess_html(&amp;$variables) {
  if ((arg(0)=='node' &amp;&amp; arg(2)=='edit') || (arg(0) == 'node') &amp;&amp; (arg(1) == 'add')) {
    $variables['classes_array'][] = 'node-edit-page';
  }
}