Select multiple random column values from a two-dimensional array

Question

I want to select 5 random ID's from my array of rows. Here is my array $test:

$test = [
    ['id' => 13, 'pets' => 8],
    ['id' => 15, 'pets' => 8],
    ['id' => 16, 'pets' => 10],
    ['id' => 17, 'pets' => 9],
    ['id' => 18, 'pets' => 10],
    ['id' => 19, 'pets' => 10],
    ['id' => 20, 'pets' => 0],
    ['id' => 21, 'pets' => 8],
    ['id' => 22, 'pets' => 9],
    ['id' => 23, 'pets' => 4],
    ['id' => 24, 'pets' => 0],
    ['id' => 40, 'pets' => 8],
    ['id' => 43, 'pets' => 2],
];

How can I select 5 random ID's from the array and put them into a string like this:

$ids = '13,17,18,21,43';

I've tried to use array_rand(), but it does not seem to work for my type of array. I'm not sure if there are any other built in PHP functions that can do this type of job or if I have to create my own function. It would be nice to have my own function like this to plug in the number of required values.

Answer 1

First extract the id column indexing also by the id, then pick 5 random ones, and finally implode into a comma separated list. Since keys must be unique, this has the added benefit of not returning duplicate ids if there happen to be duplicates in the array:

$ids = implode(',', array_rand(array_column($test, 'id', 'id'), 5));

For a function:

function array_rand_multi($array, $key, $num) {
    return implode(',', array_rand(array_column($array, $key, $key), $num));
}