title: Error using $_SERVER in a variable variable (PHP)
body: <p>I was trying to get the name of a superglobal variable through a GET parameter. I was told to pass only <code>_VAR_NAME</code> (without the <code>$</code>) in the get request, so in the program I have to access it through a variable variable: <code>$$_GET['parameter_name']</code>.</p>
  
  <p>Everything went fine except with <code>$_SERVER</code>. To try what was wrong I just did a small php script to test what was happening. Here is the code:</p>
  
  <pre><code>&lt;?php
      // ¡¡ This does not work !!
          $nombre = "_SERVER";
          $var = $$nombre;
          print_r($var);
      // This works 
          $nombre = "_GET";
          $var = $$nombre;
          print_r($var);
  ?&gt;
  </code></pre>
  
  <p>Is there any reason for the <code>_SERVER</code> version not working?
  I get the following error:</p>
  
  <blockquote>
    <p>Notice: Undefined variable: <code>_SERVER</code> in ...</p>
  </blockquote>