title: array keyword before function parameters in PHP
body: <p>I saw a function declared like this:</p>
  
  <pre><code>public static function factory($file=null, array $data=null, $auto_encode=null)
  </code></pre>
  
  <p>If you want to see the real class, please go to this <code>view.php</code> class from <a href="https://github.com/evantishuk/parser/blob/develop/classes/view.php" rel="nofollow">a fork of fuelphp parser package</a> in github.</p>
  
  <p>My question is, what does <code>array</code> keyword means in <code>array $data = null</code>?</p>