title: Putting comma(,) at end of array.Is it a convention?
body: <p>Sometimes I see arrays like the following:</p>
  
  <pre><code>
  array('item1' => array(
           'subitem1',
           'subitem2',
        )
  </code></pre>
  
  <p>Why a comma is added at end of array wheras there is not any element after submitem2?</p>