Question

我有这个数组：

Array
(
    [0] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => C4
            [price] => 53.83600000
        )

    [1] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => RE
            [price] => 53.83600000
        )

    [2] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => C4
            [price] => 0.09188900
        )

    [3] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => RE
            [price] => 0.09188900
        )

    [4] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => C4
            [price] => 584.80000000
        )

)

我期待这样的结果（按robo DESC排序）：

Array
(
    [0] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => RE
            [price] => 53.83600000
        )

    [1] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => RE
            [price] => 0.09188900
        )

    [2] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => C4
            [price] => 53.83600000
        )

    [3] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => C4
            [price] => 0.09188900
        )

    [4] => Array
        (
            [timestamp] => lm81-1527799632244
            [robo] => C4
            [price] => 584.80000000
        )

)

我已经这样做了：

    usort($dc_array_process, function($a, $b) {
        return $a['robo'] - $b['robo'];
    });

但我的数组仍未处于DESC顺序。我知道我做错了什么？

Answer 1

如果要对string值进行排序，则应使用strcmp

usort($dc_array_process, function($a, $b) {
    return strcmp($a['robo'], $b['robo']);
});

或

usort($dc_array_process, function($a, $b) {
    return -strcmp($a['robo'], $b['robo']);  //negative to reverse
});

文件：

int strcmp（string $ str1，string $ str2）

返回＆lt;如果str1小于str2，则为0; ＆GT;如果str1大于，则为0   str2，如果它们相等则为0。

Answer 2

因为算术-导致值转换为 int 。

usort($dc_array_process, function($a, $b) {
    return strcmp($a['robo'], $b['robo']);
});

Answer 3

根据the manual，传递给usort的比较函数必须......

返回小于，等于或大于零的整数

...为了正确确定订单。由于您尝试排序的值是字符串，因此您使用的减号操作无法正常工作。

尝试在返回中使用strcmp ......

return strcmp( $a['robo'], $b['robo'] );

PHP排序数组使用usort（）不工作

3 个答案: