Why is this by ref. This will be confusing. Say
```php
$ar['color'] = 'red';
$a_attr = new AttributeBagReference($a);
$ar['color'] = 'blue';
$b_attr = new AttributeBagReference($a);

if ($a_attr->getAttribute('color') == $b_attr->getAttribute('color'))
{
    echo "Weird";
}
```

Or did I miss something?