根据聚合的嵌套值将 JSON 排序为 PHP

Question

我需要：

按每个组合的总价对数组进行排序
Return只有40%总价最高.

$combinations = '[
    [                          //1st combination
        {"id":1,"price":11900},
        {"id":2,"price":499},
        {"id":3,"price":2099}
    ],
    [                          //2nd combination
        {"id":1,"price":11900},
        {"id":2,"price":499},
        {"id":4,"price":999}
    ],
    [                          //3rd combination
        {"id":1,"price":11900},
        {"id":2,"price":499},
        {"id":5,"price":899}
    ],
    [                          //4th combination
        {"id":1,"price":11900},
        {"id":2,"price":499},
        {"id":6,"price":2999}
    ]
]';

Answer 1

<?php

$json = json_decode('[
    [{"id":1,"price":11900},{"id":2,"price":499},{"id":3,"price":2099}],
    [{"id":1,"price":11900},{"id":2,"price":499},{"id":4,"price":999}],
    [{"id":1,"price":11900},{"id":2,"price":499},{"id":5,"price":899}],
    [{"id":1,"price":11900},{"id":2,"price":499},{"id":6,"price":2999}]
    ]');

// var_dump($json);

// ($a, $b) for ASC sorting
// ($b, $a) for DESC sorting
usort($json, function ($b, $a) {

    $a_prices = 0;
    foreach($a as $aa)
        $a_prices += $aa->price;

    $b_prices = 0;
    foreach($b as $bb)
        $b_prices += $bb->price;

    return $a_prices - $b_prices;
});

// Find where 40% stops
// It is up to you to choose between round(), ceil() or floor()
$breakpoint = round(sizeof($json) * 40 / 100);

$sorted_chunk = array_slice($json, 0, $breakpoint);
var_dump($sorted_chunk);

Answer 2

虽然@medilies 的回答简单而正确，但这里有一种更经济的数据排序方法。如果我们使用的是大型数据集，straight-up usort 可能会变得相当昂贵——因为每个 $a 与 [= 的比较值必须是 re-calculated 13=]比较。我们可以改为计算总和 up-front 并使用“缓存”值进行比较。

// Here's the data; decoded as an array:

$json = json_decode('[
    [{"id":1,"price":11900},{"id":2,"price":499},{"id":3,"price":2099}],
    [{"id":1,"price":11900},{"id":2,"price":499},{"id":4,"price":999}],
    [{"id":1,"price":11900},{"id":2,"price":499},{"id":5,"price":899}],
    [{"id":1,"price":11900},{"id":2,"price":499},{"id":6,"price":2999}]
    ]', true);
    
// Calculate the sums for all prices per row up-front.
// Map array into sums: Get the sum for each row's "price" columns

$sums = array_map(fn($v) => array_sum(array_column($v, 'price')), $json);

// Use $sums in our key-based sorter for the comparison values:

uksort($json, function($b, $a) use ($sums) {
    return $sums[$a] <=> $sums[$b];
});

// See the sums, get the sorted data:

var_dump($sums, $json);

这里我们使用uksort而不是usort，因为我们只需要知道被排序的数组成员的键。我们的“比较缓存”或 $sums 数组，其键与目标数组匹配，与 use() 一起传递到排序函数中。在函数内部，我们只是比较$sums[$a]和$sums[$b]中的匹配值，不重复求和计算。演示：https://3v4l.org/sNluJ#v8.1.3

在这种情况下，需要大数据集才能产生显着差异。如果需要更昂贵的迭代（例如，多次“重”函数调用）才能获得要比较的值，则“up-front 且仅一次”评估将节省很多不必要的计算周期。

关于返回 OP 想要的最终前 40% 结果，请参考已接受的答案。

根据聚合的嵌套值将 JSON 排序为 PHP

Sort JSON with PHP based on aggregated nested values

php

arrays

sorting

json