How to find a user and how to find out where there are fewer users?

Question

PHP

Hello! There is such an array

$arr = [
            'test1' => ['users' => ['test']],
            'test2' => ['users' => []],
            'test3' => ['users' => []],
            'test4' => ['users' => []]
        ];

How can I find test in this array and get the key of this array itself, that is, if I have 'test' in the 'test1' array, then I need to display this test1.

Another question is how to find where the least users are in these arrays and get the key again to add it to the users array

Answer 1

$search = 'test';

$contains = array_keys(array_filter($arr, function($item) use ($search) { return in_array($search, $item['users']); }));

print_r($contains);  // ['test1']

The key of one containing the shortest subarray 'users':

$keys = array_keys($arr);
usort($keys, function($a, $b) use ($arr) {
    return count($arr[$a]['users']) - count($arr[$b]['users']);
});

$shortest = $keys[0];