基于另一个数组保留二维数组的每一行中的元素

Question

我有这个数组：

0 => array:3 [
    "product_id" => "1138"
    "product_image" => "/resources/medias/shop/products/shop-6500720--1.png"
    "product_sku" => "6500722"
  ]
1 => array:3 [
    "product_id" => "1144"
    "product_image" => "/resources/medias/shop/products/shop-6501041--1.png"
    "product_sku" => "6501046"
  ]
2 => array:3 [
    "product_id" => "113"
    "product_image" => "/resources/medias/shop/products/shop-6294909--1.png"
    "product_sku" => "6294915"
]

我正在寻找的是一种获取仅包含所需列的多数组的方法（array_column 不是一个选项，因为它只给我 1 列）。

我做了什么

function colsFromArray($array, $keys)
{
    return array_map(function ($el) use ($keys) {
        return array_map(function ($c) use ($el) {
            return $el[$c];
        }, $keys);
    }, $array);
}

$array = array(
    [
        "product_id"    => "1138",
        "product_image" => "/resources/medias/shop/products/shop-6500720--1.png",
        "product_sku"   => "6500722"
    ],
    [
        "product_id"    => "1144",
        "product_image" => "/resources/medias/shop/products/shop-6501041--1.png",
        "product_sku"   => "6501046"
    ],
    [
        "product_id"    => "113",
        "product_image" => "/resources/medias/shop/products/shop-6294909--1.png",
        "product_sku"   => "6294915"
    ]
);
colsFromArray($array, array("product_id", "product_sku"));

//0 => array:3 [
//    "product_id" => "1138"
//    "product_sku" => "6500722"
//  ]
//1 => array:3 [
//    "product_id" => "1144"
//    "product_sku" => "6501046"
//  ]
//2 => array:3 [
//    "product_id" => "113"
//    "product_sku" => "6294915"
//]

问题是它似乎太滞后，因为它对此进行了两次迭代。如果没有此解决方法，是否有任何方法可以获取多列？

我正在使用 PHP5.6

Answer 1

如果我对你的问题理解正确，你可以试试传统的 foreach - 它可能会快一点。

function colsFromArray($array, $filterKeys) {
    $newArr = [];
    foreach($array as $val) {
       $element = [];
       foreach($filterKeys as $filterKey) {
          $element[$filterKey] = $val[$filterKey];
       }
       $newArr[] = $element;
    }
}

（未测试）

The problem is that it seems too laggy, since it iterates twice over this

您的原始代码没有在同一个数组上迭代两次。如果您想要一个数组，其中每个元素都是另一个元素数组，其中的键来自 filterKeys 数组，那么您将无法绕过主数组然后遍历 filterKeys 数组。

Answer 2

如果您需要数组中的两列，其中一列是 SKU（通常是唯一的），那么您可以将 array_column 与第三个参数一起使用。

$new = array_column($arr, "product_id", "product_sku");

这将 return 一个以 SKU 为键，ID 为值的平面数组，使该数组也易于使用。

输出：

array(3) {
  [6500722]=>
  string(4) "1138"
  [6501046]=>
  string(4) "1144"
  [6294915]=>
  string(3) "113"
}

https://3v4l.org/UDGiO

Answer 3

我认为更大的问题是你丢失了钥匙

Original Code

array (
  0 => 
  array (
    0 => '1138',
    1 => '6500722',
  ),
  1 => 
  array (
    0 => '1144',
    1 => '6501046',
  ),
  2 => 
  array (
    0 => '113',
    1 => '6294915',
 );

您可以使用一个简单的 foreach 而不是第二个 array_map:

function colsFromArray(array $array, $keys)
{
    if (!is_array($keys)) $keys = [$keys];
    return array_map(function ($el) use ($keys) {
        $o = [];
        foreach($keys as $key){
            //  if(isset($el[$key]))$o[$key] = $el[$key]; //you can do it this way if you don't want to set a default for missing keys.
            $o[$key] = isset($el[$key])?$el[$key]:false;
        }
        return $o;
    }, $array);
}

输出

array (
  0 => 
  array (
    'product_id' => '1138',
    'product_sku' => '6500722',
  ),
  1 => 
  array (
    'product_id' => '1144',
    'product_sku' => '6501046',
  ),
  2 => 
  array (
    'product_id' => '113',
    'product_sku' => '6294915',
  ),
)

Sandbox

the problem is that it seems too laggy, since it iterates twice over this.

没有不重复它 2 次的真正方法，但您可能也不想扔掉密钥。

也就是说你可以递归地取消设置你不想要的项目。

function colsFromArray(array &$array, $keys)
{
    if (!is_array($keys)) $keys = [$keys];
    foreach ($array as $key => &$value) {
        if (is_array($value)) {
            colsFromArray($value, $keys); //recursive
        }else if(!in_array($key, $keys)){
           unset($array[$key]); 
        }
    }
}

colsFromArray($array, array("product_id", "product_sku"));
var_export($array);

与之前相同的输出

通过引用更容易做到这一点。无论是否更快，您都必须测试 2 并查看。

Sandbox

最后一点，您不应该假定键存在或键将是一个数组，除非您将其强制转换为数组。

你也可以使用数组过滤器

function colsFromArray(array $array, $keys)
{
    if (!is_array($keys)) $keys = [$keys];
    $filter = function($k) use ($keys){
       return in_array($k,$keys);
    };
    return array_map(function ($el) use ($keys,$filter) {
        return array_filter($el, $filter, ARRAY_FILTER_USE_KEY );
    }, $array);
}

在循环外声明用于过滤的函数有一些小的性能优势 (array_map)。

Sandbox

Answer 4

如果您不想更改原始数组并想要您想要的输出

使用 array_insersect_key 函数得到你想要的输出如下

$array = array(
    [
        "product_id"    => "1138",
        "product_image" => "/resources/medias/shop/products/shop-6500720--1.png",
        "product_sku"   => "6500722"
    ],
    [
        "product_id"    => "1144",
        "product_image" => "/resources/medias/shop/products/shop-6501041--1.png",
        "product_sku"   => "6501046"
    ],
    [
        "product_id"    => "113",
        "product_image" => "/resources/medias/shop/products/shop-6294909--1.png",
        "product_sku"   => "6294915"
    ]
);

$keys = array("product_id"=>1, "product_sku"=>2);

$filteredArray = array_map(function($a) use($keys){
    return array_intersect_key($a,$keys);
}, $array);

print_r($filteredArray);

Answer 5

我将@Chayan 的优雅方法重构为一个函数，因此它可以像 array_column() 一样使用。要过滤的键现在可以显示为一个简单的数组。

顺便说一句，这很可能也是最快的方法，因为它使用 build-in 函数来完成大部分繁重的工作。

function array_columns(array $arr, array $keysSelect)
{    
    $keys = array_flip($keysSelect);
    return array_map(
        function($a) use($keys) {
            return array_intersect_key($a,$keys);
        },
        $arr
    );
}

$arr = [
    [
        "product_id"    => "1138",
        "product_image" => "/resources/medias/shop/products/shop-6500720--1.png",
        "product_sku"   => "6500722"
    ],
    [
        "product_id"    => "1144",
        "product_image" => "/resources/medias/shop/products/shop-6501041--1.png",
        "product_sku"   => "6501046"
    ],
    [
        "product_id"    => "113",
        "product_image" => "/resources/medias/shop/products/shop-6294909--1.png",
        "product_sku"   => "6294915"
    ]
];

$keysSelect = ["product_id" , "product_sku"];
$filteredArray = array_columns($arr, $keysSelect);

var_dump($filteredArray);

Answer 6

这是一个基于 Chayan 的重构函数，增加了对选定列的重命名：

 /** Function - array_columns  Selects columns from multidimantional array and renames columns as required
 *
 * @param  array $arr, array $selectColRenameKeys 
 *            example: (NewName1->colNameneeded1,NewName2->colNameneeded2,ect...)
 * @return array
 * @access public
 * 
 */   

 private function array_columns( $arr,$selectColRenameKeys) {    
    $keys = array_flip($selectColRenameKeys);
    $filteredArray = array_map(function($a) use($keys){
                                  $data = array_intersect_key($a,$keys);
                                  $rename_arr= array();
                                  foreach ($data as $colname => $value){
                                    $r_arr[$keys[$colname]]= $value   ;
                                  }
                                  return $r_arr;
                               }, $arr);

    return $filteredArray;
}

Answer 7

array_columns 函数的新增功能，最终追溯到 Chayan 的答案，这次是从 Joseph Mangion 的函数扩展而来。

我偶尔会有很长的选定列列表，我想在其中保留键，而不必为大量字段遵循繁琐的 ['orignal_field_name'] => ['original_field_name'] 格式。

此版本默认保留每个字段的原始键，除非指定新键。

// See answer from Joseph Mangion: 
/** Function - array_columns  Selects columns from multidimensional array and renames columns as required
*
* @param  array $in_array, array $select_columns_rename_keys
*   example of $select_columns_rename_keys:
*       ['new_column_name1' => 'original_column_name1', 'original_column_name2', 'original_column_name3', 'new_column_name4' => 'original_column_name4', ...]
*       This will use the original keys for columns 2 and 3 and rename columns 1 and 4
* @return array
* @access public
* 
*/   

public function array_columns($in_array, $select_columns_rename_keys) {
    foreach ($select_columns_rename_keys as $k => $v)
        if (is_int($k)) {
            $select_columns_rename_keys[$v] = $v;
            unset($select_columns_rename_keys[$k]);
        }
    $keys = array_flip($select_columns_rename_keys);
    $filtered_array =
        array_map(function($a) use($keys) {
        $data = array_intersect_key($a, $keys);
        $return_array = [];
        foreach ($data as $column_name => $value) $return_array[$keys[$column_name]] = $value;
        return $return_array;
    }, $in_array);

    return $filtered_array;
}

基于另一个数组保留二维数组的每一行中的元素

Preserve elements in each row of a two-dimensional array based on another array

php

arrays

filtering

php-5.6