PHP - Sorting an Associative array by another array's values

Question

I have two arrays, one is a multidimensional array which holds information, the other is a simple array which holds values for the order I want the first array in.

For example, I want my first array to be ordered by ID, by the values in the second array.

$users array:

array(3) {
    [0] => array(3) {
            'id' => 1,
            'name' => 'John Smith',
            'email' => '[email protected]',
        },
    [2] => array(3) {
            'id' => 2,
            'name' => 'Jane Smith',
            'email' => '[email protected]',
        },
    [0] => array(3) {
            'id' => 3,
            'name' => 'Jack Smith',
            'email' => '[email protected]',
        },
}

$order array:

array(3) {
    [0] => '2',
    [1] => '3',
    [2] => '1',
}

What I would like the outcome of the sorted array to be:

array(3) {
    [0] => array(3) {
            'id' => 2,
            'name' => 'Jane Smith',
            'email' => '[email protected]',
        },
    [2] => array(3) {
            'id' => 3,
            'name' => 'Jack Smith',
            'email' => '[email protected]',
        },
    [0] => array(3) {
            'id' => 1,
            'name' => 'John Smith',
            'email' => '[email protected]',
        },
}

So as you can see, I would like the array keys to be reindexed, so they are always sequential starting from 0, but for the values of each element in the $users array to be re ordered.

Answer 1

You can do this like this:

// Index users by ID
$users = array_combine(
    array_column($users, 'id'),
    $users
);

// Order the users
$users = array_map(function ($id) use ($users) {
    return $users[$id];
}, $order);

Here I used array_combine() function, that creates array by mapping given keys to values. For the keys I used all the id's in a sequential order (grabbed them with array_column()).

Having an array in such form, I can loop over $order array and grab the values from $users array by index, that actually have the value of id now.

Instead of looping with foreach I used array_map() function. If you have a collection (i.e. array) it is better to use higher order functions to process them. If you are a beginner it can be overwhelming, but you have to learn this, as this is the way things done nowadays.

Here is working example.