PHP: What are these Date (diff?) format parameters (eg. %R%a)

Question

I runned into few examples where people share code for calculating the difference between two days.

Eg.

$now = new DateTime();
$itemDate->diff($n         


        

Answer 1

r - Sign "-" when the difference is negative, empty when positive a - Total number of days as a result of a DateTime::diff() or (unknown) otherwise.

As an example,

diff($now)->format("%r%a");

echo $x;

?>

Output: string(4) "-287"