PHP5.2.17在计算小数时的有关问题

PHP5.2.17在计算小数时的问题，求救
$v['closed_price'] = 15.05;
$v['f_forecast_price'] = 14.68;
$diff = floatval($v['closed_price'] - $v['f_forecast_price']);
$closed_1 = floatval($v['closed_price']) * 0.1;
$rate = ($closed_1 - $dff) / $closed_1 ;

var_dump($closed_1 - $dff, $diff, $rate);


为什么$closed_1 - $dff是对的，但($closed_1 - $dff) / $closed_1得到一个1呢？？

理论上应该是小数才对。

为啥呢？？？

------解决方案--------------------
太不仔细了

$diff = floatval($v['closed_price'] - $v['f_forecast_price']);
$closed_1 = floatval($v['closed_price']) * 0.1;
$rate = ($closed_1 - $dff) / $closed_1 ;

var_dump($closed_1 - $dff, $diff, $rate);