Ufdjrw

I want to filter or keep selected keys and their values in a multidimensionnal array.
I tried severals methods with array_columns, array_filter, etc ... but I'm not able to keep original structure of my array.

here is original example :

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
 )
)

expected result :

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
 )
)

Someone can guide me ?

You can do it like this:

//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);

Output

//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

Pretty simple, the trick is (array) casting the object to an array, and then I like to use array_intersect_key but I am to lazy to manually do $map so I just flip the values around to be the keys.

This way you can easily add/remove keys you want to keep, just by adding/removing them from $map.

If you want to keep the inner array as an object you can cast it back too! so change this:

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

To

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

Output

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

Sandbox

To be clear all you need is this, the rest is for testing:

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

array_filter() should do the work.

Simple example:

$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]

Same example with an array of objects, supposing these have a value property:

$filtered = array_filter($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]

If your logic is about filtering from keys, the third parameter flag must be set to ARRAY_FILTER_USE_KEY. Then $item will be your keys, not values.

Similar to ArtisticPheonix's answer, loop through and keep the keys we want by using an intersection:

<?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);

Output:

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

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

)

As you have objects in your array, removing properties requires a different approach, but if you are happy to have a multidimensional array as above as the output, then you just need to cast your object to an array before the key intersection (assuming these are accessible properties).

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