[php] how to use php DateTime() function in Laravel 5

I am using laravel 5. I have try to use the

$now = DateTime();
$timestamp = $now->getTimestamp(); 

But it shows error likes this.

 FatalErrorException in ProjectsController.php line 70:
 Call to undefined function App\Http\Controllers\DateTime()

What Can I do?

I didn't mean to copy the same answer, that is why I didn't accept my own answer.

Actually when I add use DateTime in top of the controller solves this problem.

If you just want to get the current UNIX timestamp I'd just use time()

$timestamp = time(); 

Best way is to use the Carbon dependency.

With Carbon\Carbon::now(); you get the current Datetime.

With Carbon you can do like enything with the DateTime. Event things like this:

$tomorrow = Carbon::now()->addDay();
$lastWeek = Carbon::now()->subWeek();