In more object way:
$today = new \DateTimeImmutable('today');
example:
echo (new \DateTimeImmutable('today'))->format('Y-m-d H:i:s');
// will output: 2019-05-16 00:00:00
and:
echo (new \DateTimeImmutable())->format('Y-m-d H:i:s');
echo (new \DateTimeImmutable('now'))->format('Y-m-d H:i:s');
// will output: 2019-05-16 14:00:35