`usort` 未按预期对数组元素进行排序

Question

我正在使用usort 根据sales 键值上的数字对数组进行排序。这就是我所拥有的：

更正：14 不是问题，而是 9 以上。

$arr = array(

  "a" => array("sales" => 4),
  "b" => array("sales" => 3),
  "c" => array("sales" => 2),
  "d" => array("sales" => 3),
  "e" => array("sales" => 4),
  "f" => array("sales" => 14),
  "g" => array("sales" => 1)

);

$reverse_arr = $arr;

usort($reverse_arr, 'cmp');

print_r( $reverse_arr );

function cmp($a, $b) {
    return strcmp($a['sales'], $b['sales']);
}

排序对大部分部分都有效，但只有当值为14 时，它才会表现得奇怪。具有 14 个销售额的项目被放置在不应该放置的位置。这是输出：

Array
(
    [0] => Array
        (
            [sales] => 1
        )

    [1] => Array
        (
            [sales] => 14
        )

    [2] => Array
        (
            [sales] => 2
        )

    [3] => Array
        (
            [sales] => 3
        )

    [4] => Array
        (
            [sales] => 3
        )

    [5] => Array
        (
            [sales] => 4
        )

    [6] => Array
        (
            [sales] => 4
        )

)

知道为什么会发生这种情况以及如何解决这个问题吗？

Answer 1

你正在比较数字，但使用字符串比较函数来做，试试这个

function cmp($a, $b) {
    //return strcmp($a['sales'], $b['sales']);
    return $a['sales'] <=> $b['sales'];
}

结果

Array
(
    [0] => Array
        (
            [sales] => 1
        )

    [1] => Array
        (
            [sales] => 2
        )

    [2] => Array
        (
            [sales] => 3
        )

    [3] => Array
        (
            [sales] => 3
        )

    [4] => Array
        (
            [sales] => 4
        )

    [5] => Array
        (
            [sales] => 4
        )

    [6] => Array
        (
            [sales] => 14
        )