今天PHP声称 30.26 - 30.26 = -3.5527136788005E-15
我的计算器（和常识）说它应该等于0.计算中使用的两个数字都来自MySQL数据库，数据类型是varchar（255）。考虑到floatval（）这一点并不能解决问题。有谁知道这里发生了什么？
/* this is what the table looks like...
__________________________________________
|uid |AccountNumber| Total| Paid|
__________________________________________
|51 |3255 | 30.26| 30.26|
__________________________________________
*/
$q = "SELECT Total, Paid FROM Account WHERE AccountNumber='3255';";
$r = mysqli_query($db, $q);
$vars = mysqli_fetch_array($r);
$balance = floatval($vars['Total']) - floatval($vars['Paid']);
echo $balance;
输出
-3.552713678805E-15