问题
I have this array:
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"
]
What I am looking for is a way to get a multiple array with only required columns (array_column is not a option, since it's give me only 1 column).
What I have done
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"
//]
The problem is that it seems too laggy, since it iterates twice over this. Is there any way to get multiple columns without this workaround? PHP: 5.6
回答1:
I think the bigger issue is you lose the keys
Original Code
array (
0 =>
array (
0 => '1138',
1 => '6500722',
),
1 =>
array (
0 => '1144',
1 => '6501046',
),
2 =>
array (
0 => '113',
1 => '6294915',
);
You can use a simple foreach instead of the second 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;
}, $array);
}
Output
array (
0 =>
array (
'product_id' => '1138',
'product_sku' => '6500722',
),
1 =>
array (
'product_id' => '1144',
'product_sku' => '6501046',
),
2 =>
array (
'product_id' => '113',
'product_sku' => '6294915',
),
)
Sandbox
the problem is that it seems too laggy, since it iterates twice over this.
There is no real way to not iterate over it 2 times, but you probably don't want to throw away the keys either.
That said you can recursively unset the items you don't want.
function colsFromArray(array &$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);
Same output as before
This is easier to do by reference. Rather or not that is faster you'll have to test the 2 and see.
Sandbox
As a final note you shouldn't assume the key will exist or that keys will be an array unless you type cast it as an array.
You could also do it with array filter
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);
}
There is some small performance benefit to declaring the function for filtering outside of the loop (array_map).
Sandbox
回答2:
If you need two columns from an array where one is SKU (which generally is unique) then you can use array_column with the third parameter.
$new = array_column($arr, "product_id", "product_sku");
This will return a flat array with the SKU as the key and ID as value making the array easy to work with also.
Output:
array(3) {
[6500722]=>
string(4) "1138"
[6501046]=>
string(4) "1144"
[6294915]=>
string(3) "113"
}
https://3v4l.org/UDGiO
回答3:
If you do not want to change your original array and want your desired output
Use array_insersect_key function to get your desired output as following
$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);
回答4:
If I understand your question correctly, you could try a traditional foreach - it might be a little faster.
function colsFromArray($array, $filterKeys) {
$newArr = [];
foreach($array as $key => $val) {
$element = [];
foreach($filterKeys as $filterKey) {
$element[$filterKey] = $val[$filterKey];
}
$newArr[] = $element;
}
}
(Not tested)
The problem is that it seems too laggy, since it iterates twice over this
Your original code isn't iterating twice over the same array. You won't be able to get around iterating over the main array and then the filterKeys array if you want to have an array where each element is another array of elements with keys from the filterKeys array.
回答5:
I refactored the elegant approach from @Chayan into a function so it can be used like array_column(). Keys to be filtered can now be presented as a simple array.
Btw this is most likely also the fastest approach, since it uses build-in functions for most of the heavy lifting.
<?php
function array_columns(array $arr, array $keysSelect)
{
$keys = array_flip($keysSelect);
$filteredArray = array_map(function($a) use($keys){
return array_intersect_key($a,$keys);
}, $arr);
return $filteredArray;
}
$arr = 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"
]
);
$keysSelect = array("product_id" , "product_sku");
$filteredArray = array_colums($arr, $keysSelect);
var_dump($filteredArray);
回答6:
This is a refactored function based on Chayan's with added renaming of selected columns:
/** 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;
}
来源：https://stackoverflow.com/questions/52706383/php-get-multiple-columns-from-array