php date diff in days

$startDate = new DateTime("2019-10-27");
$endDate = new DateTime("2020-04-11");

$difference = $endDate->diff($startDate);
echo $difference->format("%a");

$now = time(); // or your date as well
$your_date = strtotime("2010-01-31");
$datediff = $now - $your_date;

echo round($datediff / (60 * 60 * 24));

$earlier = new DateTime("2010-07-06");
$later = new DateTime("2010-07-09");

$pos_diff = $earlier->diff($later)->format("%r%a"); //3
$neg_diff = $later->diff($earlier)->format("%r%a"); //-3