title: Undefined index error: HTTP_REFERER in Chrome but not in FireFox
body: <p>To get the right htpp/https + domain name I use <strong>$_SERVER['HTTP_REFERER']</strong>.
  It works well in FF but in Chrome I get the error: <strong>Undefined index: HTTP_REFERER</strong></p>
  
  <p>I can solve this simple to include next line in the code above by declaring </p>
  
  <pre><code>$_SERVER['HTTP_REFERER'] = '';
  </code></pre>
  
  <p>But I find it strange that this erros appears in Chrome. Or do I have to declare always $_SERVER[''] at the beginning of the function?</p>