PHP usort重新排序数组，所有的排序值都相同

问题描述：

我正在使用usort对每个元素中具有关联数组的数组进行排序.

I'm using usort to sort an array with an associative array within each element.

当我在数组中排序的所有值都相同时，它仍然会更改数组中元素的位置，是否有办法防止这种情况发生?

When all of the values I am sorting on in the array are the same then it still changes the position of the elements in the array, is there a way to prevent this?

例如:

array(
    array('name' => 'Ben', 'authn_weight' => 85.3),
    array('name' => 'Josh', 'authn_weight' => 85.3),
    array('name' => 'Fred', 'authn_weight' => 85.3)
);

可以更改为此:

array(
    array('name' => 'Josh', 'authn_weight' => 85.3),
    array('name' => 'Ben', 'authn_weight' => 85.3),
    array('name' => 'Fred', 'authn_weight' => 85.3)
);

这是排序功能:

private function weightSortImplementation($a, $b){ 
    $aWeight = $a['autn_weight'];
    $bWeight = $b['autn_weight'];

    if ($aWeight == $bWeight) {
        return 0;
    }
    return ($aWeight < $bWeight) ? 1 : -1;
}

我检查了weightSortImplementation函数是否始终返回0，表明它们相同.那么为什么仍要对数组重新排序?

I have checked that the weightSortImplementation function is always returning 0 showing that they are the same. So why is this still reordering the array?

答

啊哈，是 Schwartzian变换的案例.

它基本上包括三个步骤:

It basically consists of three steps:

排序(按照常规)
无法装饰；您反转步骤1

decorate; you turn every value into an array with the value as the first element and the key/index as the second
sort (as per normal)
undecorate; you reverse step 1

在这里(我已将其调整为您的特定用例):

Here it is (I've tweaked it to your particular use case):

function decorate(&$v, $k)
{
    $v['authn_weight'] = array($v['authn_weight'], $k);
}

function undecorate(&$v, $k)
{
    $v['authn_weight'] = $v['authn_weight'][0];
}

array_walk($a, 'decorate');
usort($a, 'weightSortImplementation');
array_walk($a, 'undecorate');

诀窍在于以下断言:

array($x, 0) < array($x, 1)

这就是保持阵列正确顺序的原因.而且，无需递归:)

This is what keeps the correct order of your array. And, no recursion required :)

PHP usort重新排序数组，所有的排序值都相同

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