Question

<?php
$VarC = 6;
$VarD = 2;
$ctA = 1;
$ctB = 2;
$VarAns = 0;
$VarAns = $ctA * ($ctB+$VarC) / $VarD;
do {
    do {
        $VarAns = $ctA * ($ctB+$VarC) / $VarD;
        echo ("X = $ctA * ($ctB + 6) / 2 is equal to: $VarAns<br>");
        $ctA = $ctA + 1;
    } while ($ctA <= 10);

    echo ("<br>");
    $ctA = 1;
    $ctB = $ctB + 2;
    $VarAns = $ctA * ($ctB+$VarC) / $VarD;
    echo ("X = $ctA * ($ctB + 6) / 2 is equal to: $VarAns<br>");
    $ctA = $ctA + 1;

} while ($ctB <= 10);

?>

我最后得到一条额外的线，我不应该得到任何想法？我试图打印并在我达到10时停止，但它会变为12！

我得到了

X = 1 * (2 + 6) / 2 is equal to: 4
X = 2 * (2 + 6) / 2 is equal to: 8
X = 3 * (2 + 6) / 2 is equal to: 12
X = 4 * (2 + 6) / 2 is equal to: 16
X = 5 * (2 + 6) / 2 is equal to: 20
X = 6 * (2 + 6) / 2 is equal to: 24
X = 7 * (2 + 6) / 2 is equal to: 28
X = 8 * (2 + 6) / 2 is equal to: 32
X = 9 * (2 + 6) / 2 is equal to: 36
X = 10 * (2 + 6) / 2 is equal to: 40

X = 1 * (4 + 6) / 2 is equal to: 5
X = 2 * (4 + 6) / 2 is equal to: 10
X = 3 * (4 + 6) / 2 is equal to: 15
X = 4 * (4 + 6) / 2 is equal to: 20
X = 5 * (4 + 6) / 2 is equal to: 25
X = 6 * (4 + 6) / 2 is equal to: 30
X = 7 * (4 + 6) / 2 is equal to: 35
X = 8 * (4 + 6) / 2 is equal to: 40
X = 9 * (4 + 6) / 2 is equal to: 45
X = 10 * (4 + 6) / 2 is equal to: 50

X = 1 * (6 + 6) / 2 is equal to: 6
X = 2 * (6 + 6) / 2 is equal to: 12
X = 3 * (6 + 6) / 2 is equal to: 18
X = 4 * (6 + 6) / 2 is equal to: 24
X = 5 * (6 + 6) / 2 is equal to: 30
X = 6 * (6 + 6) / 2 is equal to: 36
X = 7 * (6 + 6) / 2 is equal to: 42
X = 8 * (6 + 6) / 2 is equal to: 48
X = 9 * (6 + 6) / 2 is equal to: 54
X = 10 * (6 + 6) / 2 is equal to: 60

X = 1 * (8 + 6) / 2 is equal to: 7
X = 2 * (8 + 6) / 2 is equal to: 14
X = 3 * (8 + 6) / 2 is equal to: 21
X = 4 * (8 + 6) / 2 is equal to: 28
X = 5 * (8 + 6) / 2 is equal to: 35
X = 6 * (8 + 6) / 2 is equal to: 42
X = 7 * (8 + 6) / 2 is equal to: 49
X = 8 * (8 + 6) / 2 is equal to: 56
X = 9 * (8 + 6) / 2 is equal to: 63
X = 10 * (8 + 6) / 2 is equal to: 70

X = 1 * (12 + 6) / 2 is equal to: 9

最后一行X = 1 * (12 + 6) / 2 is equal to: 9不应该在那里

Answer 1

问题不在于while循环，而是你的初始代码不起作用，你使用了一个技巧。

嵌套的do / while在第一个主do / while循环中生成10行，但在后续循环中只生成9行，因此在关闭主循环之前添加了一个额外的echo以“预期”下一个循环：此回声甚至在最后一个循环中执行，然后是额外的意外行。

只需更改$ctA = 1;中的$ctA = 0;（在循环中）并删除最终的echo：

$VarC = 6;
$VarD = 2;
$ctA = 1;
$ctB = 2;
$VarAns = 0;
$VarAns = $ctA * ($ctB+$VarC) / $VarD;

do {
    do {
        $VarAns = $ctA * ($ctB+$VarC) / $VarD;
        echo ("X = $ctA * ($ctB + 6) / 2 is equal to: $VarAns<br>");
        $ctA = $ctA + 1;
    } while ($ctA <= 10);

    echo ("<br>");
    $ctA = 0;                                                   // <----------------
    $ctB = $ctB + 2;
    $VarAns = $ctA * ($ctB+$VarC) / $VarD;
    $ctA = $ctA + 1;

} while ($ctB <= 10);

的 eval.in demo

Answer 2

而不是

do {
    ....
} while (...);

做的：

while(..){
    ....
}

Answer 3

你确定它打印下面的行吗？

X = 10 * (8 + 6) / 2 is equal to: 70

X = 1 * (12 + 6) / 2 is equal to: 9

因为您的代码应输出：

X = 10 * (8 + 6) / 2 is equal to: 70

X = 1 * (10 + 6) / 2 is equal to: 8
X = 2 * (10 + 6) / 2 is equal to: 16
...
X = 10 * (10 + 6) / 2 is equal to: 80

X = 1 * (12 + 6) / 2 is equal to: 9

查看$ctA == 1和$ctB == 8时的情况。执行时输入：

do {
    $VarAns = $ctA * ($ctB+$VarC) / $VarD;
    echo ("X = $ctA * ($ctB + 6) / 2 is equal to: $VarAns<br>");
    $ctA = $ctA + 1;
} while ($ctA <= 10);

它将打印：

X = 1 * (8 + 6) / 2 is equal to: 7
...
X = 10 * (8 + 6) / 2 is equal to: 70

在内循环的最后一次迭代$ctA == 10，所以在增加1之后，现在$ctA == 11，然后它退出内部do .. while。接下来，它进入：

echo ("<br>");
$ctA = 1;
$ctB = $ctB + 2;

它打印另一个中断行，将$ ctA值重置为1.将$ ctB增加2.所以现在$ctA == 1和$ctB == 10进入：

$VarAns = $ctA * ($ctB+$VarC) / $VarD;
echo ("X = $ctA * ($ctB + 6) / 2 is equal to: $VarAns<br>");
$ctA = $ctA + 1;

打印：

X = 1 * (10 + 6) / 2 is equal to: 8

接下来，它将$ ctA值增加1，现在$ctA == 2和$ctB == 10。因此条件($ctB <= 10)变为真，外do .. while再次重复。然后它进入内循环并打印：

X = 2 * (10 + 6) / 2 is equal to: 8
...
X = 10 * (10 + 6) / 2 is equal to: 80

它退出内循环并打印另一个断行和最后一个输出

X = 1 * (12 + 6) / 2 is equal to: 9

问题是多次调用此代码：

echo ("X = $ctA * ($ctB + 6) / 2 is equal to: $VarAns<br>");

并且不会将$ ctA重置为0.

PHP，为什么我最后会得到额外的印刷品？

3 个答案: