PHP - get multiple columns from array

Question

I have this array:

0 => array:3 [
    \"product_id\" => \"1138\"
    \"product_image\" => \"/resources/medias/shop/products/shop-6500720--1.png\"
           


        

Answer 1

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);

Answer 2

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);

Answer 3

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

Answer 4

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

Answer 5

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.

Answer 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;
}