title: How to determine Referrer for external links with target="_blank"?
body: <p>I am unable to catch the Referrer using PHP:</p>
  
  <pre><code>$_SERVER['HTTP_REFERER'];
  </code></pre>
  
  <p>when visitors come to <strong>mywebsite.com</strong> from an <strong>external-web-site.com</strong> via a link with <strong>target="_blank"</strong>, for ex:</p>
  
  <pre><code>   ...    
     &lt;a href="http://mywebsite.com" target="_blank"&gt;Link to My WebSite&lt;/a&gt;
     ...
  </code></pre>
  
  <p>It always returns empty result instead of the <strong>external-web-site.com</strong></p>
  
  <p>Does it possible to correctly obtain <strong>external-web-site.com</strong>, lets say using combination of JavaScript and PHP or something else?</p>
  
  <p>Thanks in advance! </p>