函数uasort在PHP 5.5和PHP 7.0中的不同行为

在将PHP版本从5.5更改为7.0后,我遇到了Magento 1.8的奇怪行为.这种奇怪的行为是由于工作职能的改变uasort.

源代码:

 [
        "before" => ["subtotal", "grand_total"],
        "after" => [],
        "_code" => "nominal"
    ],
    "subtotal" => [
        "after" => ["nominal"],
        "before" => ["grand_total", "shipping", "freeshipping", "tax_subtotal", "discount", "tax", "weee"],
        "_code" => "subtotal"
    ],
    "shipping" => [
        "after" => ["subtotal", "freeshipping", "tax_subtotal", "nominal", "weee"],
        "before" => ["grand_total", "discount", "tax_shipping", "tax"],
        "_code" => "shipping"
    ],
    "grand_total" => [
        "after" => ["subtotal", "nominal", "shipping", "freeshipping", "tax_subtotal", "discount", "tax"],
        "before" => [],
        "_code" => "grand_total"
    ],
    "msrp" => [
        "before" => [],
        "after" => [],
        "_code" => "msrp"
    ],
    "freeshipping" => [
        "after" => ["subtotal", "nominal"],
        "before" => ["tax_subtotal", "shipping", "grand_total", "tax", "discount"],
        "_code" => "freeshipping"
    ],
    "discount" => [
        "after" => ["subtotal", "shipping", "nominal", "freeshipping", "tax_subtotal", "tax_shipping", "weee"],
        "before" => ["grand_total", "tax"],
        "_code" => "discount"
    ],
    "tax_subtotal" => [
        "after" => ["0" => "freeshipping", "1" => "subtotal", "3" => "nominal"],
        "before" => ["tax", "discount", "shipping", "grand_total", "tax_shipping", "weee"],
        "_code" => "tax_subtotal"
    ],
    "tax_shipping" => [
        "after" => ["shipping", "tax_subtotal", "subtotal", "freeshipping", "nominal"],
        "before" => ["tax", "discount", "grand_total"],
        "_code" => "tax_shipping"
    ],
    "tax" => [
        "after" => ["subtotal", "shipping", "discount", "tax_subtotal", "freeshipping", "tax_shipping", "nominal", "weee"],
        "before" => ["grand_total"],
        "_code" => "tax"
    ],
    "weee" => [
        "after" => ["subtotal", "tax_subtotal", "nominal", "freeshipping"],
        "before" => ["shipping", "tax", "discount", "grand_total", "tax_shipping"],
        "_code" => "weee"
    ]
];


function _compareTotals($a, $b)
{
    $aCode = $a['_code'];
    $bCode = $b['_code'];
    if (in_array($aCode, $b['after']) || in_array($bCode, $a['before'])) {
        $res = -1;
    } elseif (in_array($bCode, $a['after']) || in_array($aCode, $b['before'])) {
        $res = 1;
    } else {
        $res = 0;
    }
    echo sprintf("%s <> %s: %s", $aCode, $bCode, $res) . "\n";
    return $res;
}

uasort($arr, '_compareTotals');
var_dump(array_keys($arr));

在PHP 5.5中,结果是:

freeshipping <> subtotal: 1
freeshipping <> shipping: -1
weee <> freeshipping: 1
tax <> freeshipping: 1
tax_shipping <> freeshipping: 1
tax_subtotal <> freeshipping: 1
discount <> freeshipping: 1
nominal <> freeshipping: -1
freeshipping <> grand_total: -1
msrp <> freeshipping: 0
subtotal <> msrp: 0
nominal <> subtotal: -1
tax_subtotal <> shipping: -1
weee <> tax_subtotal: 1
tax <> tax_subtotal: 1
tax_shipping <> tax_subtotal: 1
grand_total <> tax_subtotal: 1
discount <> tax_subtotal: 1
shipping <> tax_subtotal: 1
grand_total <> discount: 1
grand_total <> shipping: 1
grand_total <> tax_shipping: 1
grand_total <> tax: 1
weee <> grand_total: -1
shipping <> discount: -1
tax <> shipping: 1
tax_shipping <> shipping: 1
weee <> shipping: -1
tax_shipping <> discount: -1
tax <> tax_shipping: 1
discount <> tax_shipping: 1
tax <> discount: 1

array(11) {
  [0] =>
  string(7) "nominal"
  [1] =>
  string(8) "subtotal"
  [2] =>
  string(4) "msrp"
  [3] =>
  string(12) "freeshipping"
  [4] =>
  string(12) "tax_subtotal"
  [5] =>
  string(4) "weee"
  [6] =>
  string(8) "shipping"
  [7] =>
  string(12) "tax_shipping"
  [8] =>
  string(8) "discount"
  [9] =>
  string(3) "tax"
  [10] =>
  string(11) "grand_total"
}

在PHP 7.0中,结果是:

nominal <> subtotal: -1
subtotal <> shipping: -1
shipping <> grand_total: -1
grand_total <> msrp: 0
msrp <> freeshipping: 0
freeshipping <> discount: -1
discount <> tax_subtotal: 1
msrp <> tax_subtotal: 0
freeshipping <> tax_subtotal: -1
discount <> tax_shipping: 1
freeshipping <> tax_shipping: -1
tax_subtotal <> tax_shipping: -1
discount <> tax: -1
tax <> weee: 1
tax_shipping <> weee: 1
freeshipping <> weee: -1
tax_subtotal <> weee: -1

array(11) {
  [0] =>
  string(7) "nominal"
  [1] =>
  string(8) "subtotal"
  [2] =>
  string(8) "shipping"
  [3] =>
  string(11) "grand_total"
  [4] =>
  string(4) "msrp"
  [5] =>
  string(12) "freeshipping"
  [6] =>
  string(12) "tax_subtotal"
  [7] =>
  string(4) "weee"
  [8] =>
  string(12) "tax_shipping"
  [9] =>
  string(8) "discount"
  [10] =>
  string(3) "tax"
}

在PHP5中grand_total是最后一个元素,但在PHP7中 - 没有.问题与位置msrp元素的不确定性有关.我找到了与php 5相关的这个主题的研究.

我通过指出相对位置来解决这个问题msrp.但我想知道为什么它在php5中工作,并且在php7中不起作用.这些是新版本的php或bug的功能？

另外#1

问题不仅在于PHP7不知道如何对相等的元素进行排序,例如msrp和grand_total.如果你看一下项目shipping和freeshipping,然后他们都有明确的规定,谁应该更早.PHP5解决了这个问题,PHP7没有.

1> NikiC..：

---

从usort()文档:

注意:如果两个成员比较相等,则它们在排序数组中的相对顺序是未定义的.

这就是你在这里看到的.PHP 7使用不同的,部分稳定的排序算法,因此根据您的排序函数进行比较的元素现在可能具有不同的顺序.

如果你关心相等元素的排序顺序(这不仅仅是一个测试问题),你应该在比较函数中明确它.

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@danil,如果你说某些东西是相同的,那么PHP就无法对你的数组进行正确的排序.因为你的函数对于某些不相等的东西返回0,所以它会混淆剩下的那种.

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这基本上是[GIGO原则](https://en.wikipedia.org/wiki/Garbage_in,_garbage_out)的情况:如果你给排序函数废话,你会得到废话.