title: Use array value while declaring an array in PHP
body: <p>I was wondering...is it possible to use a value from an array which is currently being declared? Something like:</p>
  
  <pre><code>$a = array(
      'foo' =&gt; 'value',
      'bar' =&gt; $a['foo']
  );
  </code></pre>
  
  <p>This is only a simple example. It would be pretty useful doing this, since it frees you from doing extra manipulation after the array declaration.</p>