php – 绝对参数在DateTime :: diff中做了什么(DateTime [,bool

$c = new DateTime();
$o = clone $c;
$o->modify('-60 days');
$diff = $c->diff($o);
$diff2 = $c->diff($o,TRUE);
var_dump($diff,$diff2);

哪个输出

object(DateInterval)#3 (8) {
  ["y"]=> int(0),["m"]=> int(1),["d"]=> int(29),["h"]=> int(0),["i"]=> int(0),["s"]=> int(0),["invert"]=> int(1),["days"]=> int(60)
}
object(DateInterval)#4 (8) {
  ["y"]=> int(0),["invert"]=> int(0),["days"]=> int(60)
}

正如我所看到的,只有“反转”属性发生了变化.这是什么意思？