title: $_SERVER['HTTP_ORIGIN'] doesn't work
body: <p>When I use <code>$_SERVER['HTTP_ORIGIN']</code>.</p>
  
  <pre class="lang-html prettyprint-override"><code>echo $_SERVER['HTTP_ORIGIN'] ;
  </code></pre>
  
  
  
  <p>Return
  Notice: Undefined index: HTTP_ORIGIN in D:\xampp\htdocs\safe\test.php on line 12</p>
  
  <p>What is Wrong?!</p>