title: Using PHP $_SERVER[HTTP_REFERER] to display custom welcome messages/content
body: <p>I'm trying to display a custom welcome message to visitors based off what social media site they are coming in from. I can't get this string to work but it is echoing back no matter what the refering site is. Can anyone help me get this to work? Many thanks!</p>
  
  <pre><code>&lt;?php 
  if (strpos("twitter.com",$_SERVER[HTTP_REFERER])==0) {
      echo "Welcome, Twitter User! If you enjoy this post, don't hesitate to retweet it to your followers"; 
  } 
  ?&gt;
  </code></pre>
  
  <p>Tried using </p>
  
  <pre><code>&lt;?php 
  if(isset($_SERVER['HTTP_REFERER'])) {
      echo $_SERVER['HTTP_REFERER'];
  }
  ?&gt;
  </code></pre>
  
  <p>to get this to work but no luck.</p>