打印正/负date_diff

Question

Say I have this:

$date1=date_create(date('H:I', strtotime('8:00')));
$date2=date_create(date('H:I', strtotime('18:00')));
$diff1=date_diff($date1,$date2);

echo $diff1->format("%h:%I");

which outputs 10:00 (hours), but now i want to compare this:

$date3=date_create(date('H:I', strtotime('8:30')));
$date4=date_create(date('H:I', strtotime('17:45')));
$diff2=date_diff($date3,$date4);

echo $diff2->format("%h:%I");

which outputs 9:15. So, how can I have the diff and the sign (if it's negative) between $diff1 and $diff2? I just want to get that 45 minutes negative (in this case).

Answer 1

You can use %r to format to print if the difference is negative:

$diff1 = date_diff(date_create(date('H:i', strtotime('20:00'))), date_create(date('H:i', strtotime('18:00'))));
echo $diff1->format("%r%H:%i"); // prints -02:00

$diff2 = date_diff(date_create(date('H:i', strtotime('8:30'))), date_create(date('H:i', strtotime('17:45'))));
echo $diff2->format("%r%H:%i"); // prints 09:15

A better version:

$diff1 = date_diff(DateTime::createFromFormat('H:i', '20:00'), DateTime::createFromFormat('H:i', '18:00'));
echo $diff1->format("%r%H:%i"); // prints -02:00

$diff2 = date_diff(DateTime::createFromFormat('H:i', '8:30'), DateTime::createFromFormat('H:i', '17:45'));
echo $diff2->format("%r%H:%i"); // prints 09:15

Read more about DateTime.