Array class property
<p>This code gives the error "unexpected '.', expecting ')'".  Why is this invalid?  I'd thought that as both parts are constant, I could concatenate them.  New to PHP.  Thanks.</p>

<pre><code>class c {
  const HELLO = 'hello';
  public $arr = array(
    'hw' =&gt; self::HELLO . 'world'
  );
}
</code></pre>
