除以100时的PHP舍入问题

我有一个来自数组的值，需要转换为百分比。我的问题是，当我除以100时，我似乎失去了小数点后的数字。例如，我需要56.5才能变成.565，这就是.56。

我试过使用round（）number_format（）等，但都没有用。

$yearnow = date("Y");
$ratedate = $mileagerates->Rates->Year;
$rateamount = $mileagerates->Rates->Mileage_Rate;
if ($yearnow == $ratedate) {
  $currentyear = $ratedate;
  $currentamount = $rateamount / 100;
} else {
  $currentyear = "";
  $currentamount = 0;
}
echo $currentyear;
echo $currentamount;