PHP filter array by another true/false array

Question

I have this array:

$arr_to_filter = array(1, 3, 5, 7, 10, 12, 15);
$filter = array(0, 1, 1, 0, 1);

Expected result:

Array ( 
       [0] => 3 
       [1] => 5 
       [2] => 10 
)

I can achieve this by this loop:

$arr_to_filter = array(1, 3, 5, 7, 10, 12, 15);
$filter = array(0, 1, 1, 0, 1);
$output_array = array();

foreach($arr_to_filter as $key=>$val) {
   if(isset($filter[$key]) && $filter[$key]) {
       $output_array[] = $val;
   }
}

print_r($output_array);

Can i achieve this using built in functions like array_filter or another built in function without using loops?

"Built in functions like array_***" are made with loops.

Casimir et Hippolyte
– Casimir et Hippolyte

2017-05-24 20:52:12 +00:00
Commented May 24, 2017 at 20:52 — Casimir et Hippolyte
– Casimir et Hippolyte, Commented May 24, 2017 at 20:52

Barmar · Accepted Answer · 2017-05-24 21:06:03Z

3

If you're using PHP >= 5.6, you can take advantage of array_filter()'s third argument, allowing you to match keys with your filter set:

$arr_to_filter = array(1, 3, 5, 7, 10, 12, 15);
$filter = array(0, 1, 1, 0, 1);

$result = array_filter(
    $arr_to_filter,
    function($key) use ($filter) {
        return !empty($filter[$key]);
    },
    ARRAY_FILTER_USE_KEY
);

var_dump($result);

If you're using an earlier version of PHP, then you need to filter on the keys, and intersect that result against your original array:

$result = array_intersect_key(
    $arr_to_filter,
    array_filter(
        array_keys($arr_to_filter),
        function($key) use ($filter) {
            return !empty($filter[$key]);
        }
    )
);

If you want to reset the keys after either of these methods, then just use array_values()

edited May 24, 2017 at 21:06

Barmar

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answered May 24, 2017 at 20:54

Mark Baker

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Comments

RomanPerekhrest · Accepted Answer · 2017-05-24 21:11:49Z

1

The solution using array_map, array_slice and array_reduce functions:

$filtered = array_reduce(array_map(null, array_slice($arr_to_filter, 0, count($filter)), $filter),
    function($r, $a){
        if ($a[1]) $r[] = $a[0];
        return $r;
    }, []);

print_r($filtered);

The output:

Array
(
    [0] => 3
    [1] => 5
    [2] => 10
)

answered May 24, 2017 at 21:11

RomanPerekhrest

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1 Comment

RomanPerekhrest Over a year ago

@semsem, actually, your foreach loop approach is not so bad in such case

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