php中DateTime、diff

$january = new DateTime('2010-01-01');
$february = new DateTime('2010-02-01');
$interval = $january->diff($february);

// %a will output the total number of days.
echo $interval->format('%R%a total days'). '<br/>';// +31 total days

// While %d will only output the number of days not already covered by the
// month.
echo $interval->format('%m month, %d days');// 1 month, 0 days

format

format