title: PHP include not executing code
body: <p>I have an include in the head of my php file:</p>
  
  <pre><code>include 'scripts/tracking_code.php';
  </code></pre>
  
  <p>In there, I run a basic test with if/else and echo some basic text.</p>
  
  <p>Problem is that nothing is getting printed to screen.</p>
  
  <p>I then just tried to print something a little more basic... The tracking_code.php now simply includes this:</p>
  
  <pre><code>echo "&lt;!-- This is the file --&gt;";
  </code></pre>
  
  <p>Still nothing?</p>
  
  <p>I know the include is getting included because when I turn E_ALL error reporting, the $_GET[] call throws a "Notice: Undefined index:"</p>
  
  <p>Here is my original code (before simply replacing with "echo" (as above))</p>
  
  <pre><code>&lt;?php
  
  $trackingid = $_GET['trackingid'];
  
  if ( !empty( $trackingid ) ) {
      echo "&lt;!-- trackingid: $trackingid --&gt;";
  } else { 
      echo "&lt;!-- trackingid is empty --&gt;";
  }
  ?&gt;
  </code></pre>
  
  <p>Yet nothing is ever printed?</p>
  
  <p>What am I missing?</p>