ลบเวลา 2019-08-01 09:50 - 2019-08-01 10:00 = ใช้เวลา ไป 10 นาที

$startTime = '2019-08-01 09:50:00';
$endTime = '2019-08-01 10:00:00';
echo 'start: ' . $startTime . '<br>' . PHP_EOL;
echo 'end: ' . $endTime . '<br>' . PHP_EOL;


$Dt1 = new \DateTime($startTime);
$Dt2 = new \DateTime($endTime);
$Interval = $Dt1->diff($Dt2);
echo $Interval->format('%R%I') . ' minutes.<br>' . PHP_EOL;

$startTime = date('Y-m-d H:i:s');// สมมุติ 2019-08-04 20:00:02
$endTime = '2019-08-04 20:30:00';
echo 'start: ' . $startTime . '<br>' . PHP_EOL;
echo 'end: ' . $endTime . '<br>' . PHP_EOL;


$Dt1 = new \DateTime($startTime);
$Dt2 = new \DateTime($endTime);
$Interval = $Dt1->diff($Dt2);
echo $Interval->format('%R%I') . ' minutes.<br>' . PHP_EOL;

echo 'set seconds to zero.<br>' . PHP_EOL;
$Dt1->setTime($Dt1->format('H'), $Dt1->format('i'), 0);
$Interval = $Dt1->diff($Dt2);
echo $Interval->format('%R%I') . ' minutes.<br>' . PHP_EOL;