title: XPath get node by value
body: <p>I have this XML:</p>
  
  <pre><code>&lt;root&gt;
    &lt;experiment accessCount="1" downloadCount="1"&gt;alfa&lt;/experiment&gt;
    &lt;experiment accessCount="1" downloadCount="1"&gt;beta&lt;/experiment&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p>And I would like to detect if the node experiment with value alfa exists.
  But this PHP code is returning to me all values. </p>
  
  <pre><code>    $this-&gt;xml = simplexml_load_file("data/stats.xml") or die("Error: Cannot create object");
      $node = $this-&gt;xml-&gt;xpath("/root[experiment='alfa']");
  </code></pre>
  
  <p>Where am I wrong?</p>