Why DateTime diff wrong result : I have the following code that is returning the wrong answer. Please let me know what's wrong.

    $start_date  = new DateTime('31-03-2019');
    $end_date    = new DateTime('01-05-2019');
    $d = $start_date->diff($end_date);
    echo "day: " . $d->d . " month: " . $d->m . "\n";

It is returning the wrong answer.

    day: 0 month: 1

I expect the answer to be 

    day: 1 month: 1

