Concatenate instance variables
<p>I can't figure out why I get this error:</p>

<blockquote>
  <p>Parse error: syntax error, unexpected '.', expecting ',' or ' in Settings.php on line 5</p>
</blockquote>

<p>Here is the code </p>

<p>

<pre><code>class Settings
{
    public $appDir = 'app';
    public  $controllersDir = $appDir . '/controllers';

}
</code></pre>
