我正在做一个与数据库一起工作的实验，我得到了这个奇怪的结果。
系统是这样的：我有一个按钮，每次你点击它时，计数器都会加 1。一旦达到一定数量，它会计算分数扣除并更新分数
PHP：
$counter = $_POST['counter'];
$user = $_POST['user'];
$sql = "SELECT score FROM board WHERE player = '$user'";
$result = mysqli_query($con,$sql);
$row = mysqli_fetch_array($result);
if($counter == 1)
$divisor = 0;
else if($counter == 5)
$divisor = 0.1;
else if($counter == 20)
$divisor = 0.3;
else if($counter == 50)
$divisor = 1;}
$deduction = $row['score'] * $divisor;
$sql = "UPDATE board SET score = score - ".$deduction." WHERE player = '$user'";
我从 score = 10 开始，这些是结果
Score: 10
Counter: 1
Divisor = 0; Deduction = 10 * 0;
UPDATE ... score = score - Deduction (0)
New score = 10
-------------------------------------
Score: 10
Counter: 5
Divisor = 0.1; Deduction = 10 * 0.1;
UPDATE ... score = score - Deduction (1)
New score = 9
-------------------------------------
Score: 9
Counter: 20
Divisor = 0.3; Deduction = 9 * 0.3;
UPDATE ... score = score - Deduction (2.7)
New score = 6.3
-------------------------------------
## Here is the curious part
Score: 6.3
Counter: 50
Divisor = 1; Deduction = 6.3 * 1;
UPDATE ... score = score - Deduction (6.3)
New score = 0.000000190735
知道为什么我得到0.000000190735吗？我现在真的有点困惑。
巴格兹，
评论有点长。
毫无疑问，这是由查询的字符串的不同表示score和/$divisor或转换为$divisor字符串引起的。很难准确指出问题出在哪里，因为有几个不同的地方。
如果你真的需要处理这个，在数据库中进行计算：
UPDATE board
SET score = score * (1 - ?)
WHERE player = ?;
将占位符作为参数传入——而不是修改查询字符串。
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