title: Will require_once and include_once together include the file twice?
body: <p>If I have this:</p>
  
  <pre><code>require_once('myfile.php');
  </code></pre>
  
  <p>then later:</p>
  
  <pre><code>include_once('myfile.php');
  </code></pre>
  
  <p>Will the file get included again or just the once?</p>
  
  <p>Also what is the difference between the two? Require causes an error on failure and include tries to recover? any other differences?</p>