title: Statements with and without parentheses
body: <p>I'm currently learning PHP, and I've seen a couple of commands written with, and some without parentheses. I've had a look online but I could not seem to find an explanation as to why.</p>
  
  <p>The sort of thing I'm talking about is:</p>
  
  <pre><code>include "header.php";
  </code></pre>
  
  <p>vs:</p>
  
  <pre><code>include ("header.php");
  </code></pre>
  
  <p>I've also seen the same thing with <code>echo</code> commands. Could someone explain the differences of these to me?</p>