使用另一个数组的键值获取数组的值

Question

I have an array with some values (numeric values):

$arr1 = [1, 3, 8, 12, 23]

and I have another associative array that a key (which matches to a value of $arr1) correspond to a value. This array may contain also keys that don't match with $arr1.

$arr2 = [1 => "foo", 2 => "foo98", 3 => "foo20", 8 => "foo02", 12 => "foo39", 15 => "foo44", 23 => "foo91", 34 => "foo77"]

I want as return the values of $arr2 specifying as key the values of $arr1:

["foo", "foo20", "foo02", "foo39", "foo91"]

If possible, all this, without loops, using just PHP array native functions (so in an elegant way), or at least with the minimum number of loops possible.

Answer 1

Minimal loop is simple - 1. as:

foreach($arr1 as $k) {
    $res[] = $arr2[$k];
}

You can do that with array_walk but I think this simple way is more readable.

If you insist you can do with array_filter + array_values + in_array as:

$res = array_values(array_filter($arr2,
    function ($key) use ($arr1) { return in_array($key, $arr1);},
    ARRAY_FILTER_USE_KEY
));

You can see this for more about filtering keys