title: how to use $_GET with this url format site.com/extension/rar
body: <p>I am seeing this url format at most websites.</p>
  
  <pre><code>site.com/extension/rar
  </code></pre>
  
  <p>I wonder how they get the value='rar' using $_GET.</p>
  
  <p>What I know is that $_GET can be use in here</p>
  
  <pre><code>site.com/extension/index.php?ext=rar
  </code></pre>
  
  <p>Now I wanted to change my way of calling a variable.</p>
  
  <p>I wanted to apply what most websites do.</p>
  
  <p>How can I call variable in the former?</p>