Question

我想过滤或将选定键及其值保留在多维数组中。我用array_columns，array_filter等尝试了几种方法，但是我无法保留数组的原始结构。

这是原始示例：

Array
(
    [0] => Object
        (
            [not_wanted_key1] => some value
            [wanted_key1] => wanted value
            [wanted_key2] => wanted value
            [not_wanted_key3] => some value
            [wanted_key3] => wanted value



       )

    [1] => Object
        (
            [not_wanted_key1] => some value
            [wanted_key1] => wanted value
            [wanted_key2] => wanted value
            [not_wanted_key3] => some value
            [wanted_key3] => wanted value
        )
)

预期结果：

Array
(
    [0] => Object
        (
            [wanted_key1] => wanted value
            [wanted_key2] => wanted value
            [wanted_key3] => wanted value
       )

    [1] => Object
        (
            [wanted_key1] => wanted value
            [wanted_key2] => wanted value
            [wanted_key3] => wanted value
        )
)

有人可以指导我吗？

Answer 1

array_filter()应该会做。

简单的例子：

$original = ['a' => 2, 'b' => 5, 'c' => 6];

$filtered = array_filter($original, function($item) {
    // This anonymous function must return true for keeping your item, or false for not keeping it

    // There I want to keep items with a value more than 4.
    return ($item > 4);
});

// Output of $filtered: ['b' => 5, 'c' => 6]

与对象数组相同的示例，假设它们具有value属性：

$filtered = array_filter($original, function($item) {
    // There I want to keep items with a value more than 4.
    return ($item->value > 4);
});

// Output of $filtered: ['b' => 5, 'c' => 6]

如果您的逻辑与从键过滤有关，则必须将第三个参数flag设置为ARRAY_FILTER_USE_KEY。然后$item将是您的键，而不是值。

Answer 2

您可以这样做：

//test data
$array[] = new stdClass;
$array[0]->not_wanted_key1 = '1';
$array[0]->not_wanted_key2 = '3';
$array[0]->wanted_key1 = '4';
$array[0]->wanted_key2 = '5';
$array[0]->wanted_key3 = '6';

print_r($array);


$map = array_flip(['wanted_key1', 'wanted_key2', 'wanted_key3']);

$res = array_map(function($item) use ($map){
    return array_intersect_key((array) $item, $map);
}, $array);


print_r($res);

输出

//input array
Array
(
    [0] => stdClass Object
        (
            [not_wanted_key1] => 1
            [not_wanted_key2] => 3
            [wanted_key1] => 4
            [wanted_key2] => 5
            [wanted_key3] => 6
        )

)
//output array
Array
(
    [0] => Array
        (
            [wanted_key1] => 4
            [wanted_key2] => 5
            [wanted_key3] => 6
        )

)

Sandbox

非常简单，诀窍是(array)将对象转换为数组，然后我喜欢使用array_intersect_key，但是我懒于手动执行$map，所以我只需要翻转值是关键。

通过这种方式，您可以轻松地添加/删除要保留的密钥，只需从$map中添加/删除它们即可。

如果您想将内部数组保留为对象，也可以将其转换回！所以改变这个：

 return array_intersect_key((array) $item, $map);

收件人

 return (object)array_intersect_key((array) $item, $map);

输出

Array
(
    [0] => stdClass Object
        (
            [wanted_key1] => 4
            [wanted_key2] => 5
            [wanted_key3] => 6
        )
)

Sandbox

为清楚起见，您所需要做的就是这些，其余的用于测试：

$map = array_flip(['wanted_key1', 'wanted_key2', 'wanted_key3']);
$res = array_map(function($item)use($map){return array_intersect_key((array)$item,$map);},$array);

Answer 3

类似于ArtisticPheonix的答案，使用交集循环遍历并保留我们想要的键：

<?php

$data =
[
    ['fruit'=>'apple',  'veg'=>'carrot'],
    ['fruit'=>'banana', 'veg'=>'marrow']
];

$flipped_wanted_keys = array_flip(['fruit']);
foreach($data as &$item)
    $item = array_intersect_key($item, $flipped_wanted_keys);

unset($item);
print_r($data);

输出：

Array
(
    [0] => Array
        (
            [fruit] => apple
        )

    [1] => Array
        (
            [fruit] => banana
        )

)

由于数组中有对象，因此删除属性需要使用不同的方法，但是如果您希望将上述多维数组作为输出，则只需将对象转换为键交点之前的数组即可（假设这些是可访问的属性。

$item = array_intersect_key((array) $item, $flipped_wanted_keys);

将多维数组的特定键和值提取或过滤到另一个数组

3 个答案: