For循环分配错误的数组索引

Question

我正在尝试创建一个具有以下结构的数组：

[10] => Array
    (
        [10] => test key
        ...
        [100] => test key
    )

[20] => Array
    (
        [10] => test key
        ...
        [100] => test key
    )

[30] => Array
    (
        [10] => test key
        ...
        [100] => test key
    )
...

这是我用来创建这样的结构的循环：

$array = array();
for ($x = 0.1; $x <= 1; $x+=0.1) {
    $index = $x*100;
    for ($z = 10; $z <= 100; $z+=10) {
        $array[(int)$index][$z] = 'test key';
    }
}

不幸的是，一旦它应该达到90和100索引，我收到的输出就像这样：

[80] => Array
    (
        [10] => test key
         ...
        [100] => test key
    )

[89] => Array
    (
        [10] => test key
         ...
        [100] => test key
    )

[99] => Array
    (
        [10] => test key
         ...
        [100] => test key
    )

为什么计算指数为89和99？不应该分别是90和100吗？

*编辑 我使用花车作为我们用来进行一些计算的百分比的测量。我知道我也可以增加10个增量，但这需要我最终再次除以100以获得浮动

Answer 1

不确定为什么要使用$x的浮动广告...只需从10开始，然后逐步10，直至找到100。

$array = array();
for ($x = 10; $x <= 100; $x+=10) {
    $f = ((float)$x) / 100.0; # calculate float value here
    for ($z = 10; $z <= 100; $z+=10) {
        $array[$x][$z] = 'test key';
    }
}

正如其他人所指出的那样，你所看到的很可能是由于浮点运算舍入。

Answer 2

为什么计算指数为89和99？不应该分别是90和100？

我认为这是因为您使用小数作为x值，为什么不使用整数值？

$array = array();
for ($x = 10; $x <= 100; $x+=10) {
    for ($z = 10; $z <= 100; $z+=10) {
        $array[$x][$z] = 'test key';
    }
}

Answer 3

稍微更现代的语法：

<?php

$array = [];
for ($x = 10; $x <= 100; $x+=10) {
    for ($z = 10; $z <= 100; $z+=10) {
        $array[$x][$z] = 'test key';
    }
}

print_r($array);
?>

输出：

Array
(
    [10] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [20] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [30] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [40] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [50] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [60] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [70] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [80] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [90] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

    [100] => Array
        (
            [10] => test key
            [20] => test key
            [30] => test key
            [40] => test key
            [50] => test key
            [60] => test key
            [70] => test key
            [80] => test key
            [90] => test key
            [100] => test key
        )

)