laravel/framework — pull request #1165 by Ruby184 (2013-05-04 00:01:45+00:00)
Title: Added ability to pass Closure to union statement in query builder

Example:
```php
$users = DB::table('users')->whereNull('last_name')->union(function($q)
{
$q->from('users')->whereNull('first_name');
})->get();
```