title: Echo alternative $_GET request method
body: <p>I'm aware of this method:</p>
  
  <pre><code>stackoverflow.com/?id=stack
  
  &lt;?php 
     echo $_GET['id'];
     //output: stack
  ?&gt;
  </code></pre>
  
  <p>But I would like to know how to get $_GET request if url is like this:</p>
  
  <pre><code>stackoverflow.com/?stack
  
  &lt;?php 
     echo ???
     //output: stack
  ?&gt;
  </code></pre>
  
  <p>Notice that content after <code>/?</code> is dynamically changed.</p>