title: Is xsi:nil to be true is empty or null?
body: <p>As per the spec,  An element may be ·valid· without content if it has the attribute xsi:nil with the value true. so for example, </p>
  
  <pre><code>&lt;root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"&gt;
     &lt;e1 xsi:nil="true"&gt;&lt;/e1&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p>If I am checking if the element (e1) contains text or not by something like: <code>$e1=''</code> for null elements so will the above xml return true or not? I believe its okay to check if the element is empty or not with xsi:nil and the above will return false.</p>