I disagree. In this case, I loose the key name. I.E.

```php
$array = array(
    'root1'  =>  array('property1' => 'message1'),
    'root2'  =>  array('property2' => 'message2'),
);

//$output = $output[$root] returns the following:
$array = array('property1' => 'message1');

//$output = array_intersect_key($output, array($root => 0)) returns the following:
$array = array('root1' => array('property1' => 'message1'));
```