title: Query string of referrer URL
body: <p>Using php or javascript or regex, is there a quick (one-liner hopefully) to get the query string from the previous (referrer) URL?</p>
  
  <p>Example,</p>
  
  <p>User is at </p>
  
  <pre><code>www.sample.com?one
  </code></pre>
  
  <p>Then clicks link to go to </p>
  
  <pre><code>www.sample.com?two
  </code></pre>
  
  <p>From page two... I want to know the previous query string "one." </p>