根据属性值有效地查找嵌套的PHP数组元素 [英] Efficiently find nested PHP array element based on attribute value

问题描述

假设一个PHP数组在转换为JSON时具有以下格式：

Suppose a PHP array, when cast to JSON, has the following format:

[{
    "key": "width",
    "value": "1200",
    "label": "Width (mm)",
    "choice": ""
},
{
    "key": "height",
    "value": "900",
    "label": "Height (mm)",
    "choice": ""
},
{
    "key": "material",
    "value": "paper",
    "label": "Material",
    "choice": "Paper"
}]

（这是一个

让我们假设我想有效地找到所使用的材料。换句话说，我想搜索一个嵌套数组，该数组的 key 值 material ，并且我想返回值，该值将是纸。

Let's suppose I want to efficiently find what material is used. In other words, I want to search for a nested array that has for key the value material, and I want to return the value which would be paper.

I知道这可以通过使用foreach / while循环来完成，但是PHP丰富了我不太熟悉的编译数组函数。在这里使用的最佳功能是什么？

I know this can be done by using a foreach/while loop, but PHP is rich with compiled array functions that I'm not very familiar with. What's the best function to use here?

更新：到目前为止，我已经尝试过了

到目前为止，我尝试过两件事：

Here's two things I've tried so far:

尝试＃1：

$json = '[{"key":"width","value":"1200","label":"Width (mm)","choice":""},{"key":"height","value":"900","label":"Height (mm)","choice":""},{"key":"material","value":"paper","label":"Material","choice":"Paper"}]';
$array = json_encode($json, true);
$material = '';
foreach($array as $nestedArray) {
  if($nestedArray['key'] = 'material') {
    $material = $nestedArray['value'];
  }
}

尝试＃2：

$json = '[{"key":"width","value":"1200","label":"Width (mm)","choice":""},{"key":"height","value":"900","label":"Height (mm)","choice":""},{"key":"material","value":"paper","label":"Material","choice":"Paper"}]';
$array = json_decode($json, true);
$filteredArray = array_filter($array, function($array) {
    return ($array['key'] == 'material');
});
$arr = array_pop($filteredArray)['value'];

---

两者都产生正确的值，但＃1是混乱，并且＃2可能不是PHP数组函数的最佳使用。

---

Both produce the right value, but #1 is messy, and #2 may not be the best use of PHPs array functions.

推荐答案

这取决于您要除了找到价值之外还可以做。

array_filter 很简单，但是它将遍历整个数组。

array_filter is simple, but it will loop through the whole array.

array_search 看起来更快，但是它需要复制源数组，因此实际上是 比 array_filter 慢（不是很多）。

array_search on a reduced set looks faster, but it needs to make a copy of the source array, so it's actually slower than array_filter (not by much).

foreach <您首先尝试过的/ code>解决方案不会创建额外的数组，它使您无法进行查找：

The foreach solution you tried first will not create extra arrays and it allows you to break on a find:

foreach($array as $nestedArray) {
    if ($nestedArray['key'] == 'material') {
        $material = $nestedArray['value'];
        break; // <--- found!
    }
}

所以在短数组上，我会接受使用 array_column 的解决方案，或者如果您确定材料在那里，则可以进行以下 array_column 调整：

So on short arrays I'd go with the accepted solution using array_column, or if you're sure that the material is there, there is this array_column tweak:

// Transform the records into keypairs
$keypairs = array_column($records, 'value', 'key');

现在的密钥对是[width => 900，material => paper，...]，所以：

Now keypairs is [ width => 900, material => paper, ... ], so:

$material = $keypairs['material'];

我要添加 array_key_exists 确定。这样可以节省 array_search （不是一个很大的优势，但是您可能会使用keypair对象）。

I'd add a array_key_exists just to be sure. This saves the array_search (not that great an advantage, but you might have a use for the keypair object).

如果您只需要一个值而不需要其他任何内容，那么性能就非常重要，并且数组很大，那么我不会放弃在JSON内将' material：'作为字符串使用 strpos ，即使它是代码气味。

If you need exactly that one value and nothing else, performance is at a premium, and the array is large, I'd not throw out the idea of looking for '"material":"' inside the JSON as a string with strpos, even if it's a code smell.

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