Sorting array for every child coming after parent

Question

I have an array like that:

 1,
        \'parent_id\' => null
    ),
    array(
        \'id\' => 2,
             


        

Answer 1

This working solution works with array_multisort().

Try with:

$data = array(
    array(
        'id' => 1,
        'parent_id' => null
    ),
    array(
        'id' => 2,
        'parent_id' => 1
    ),
    array(
        'id' => 3,
        'parent_id' => null
    ),
    array(
        'id' => 4,
        'parent_id' => 2
    )
);

$parent_ids = array();
foreach ($data as $item) {
    $parent_ids[]  = $item['parent_id'];
}

array_multisort($parent_ids, SORT_ASC, $data);

If you want null values to be at the end replace that foreach with:

foreach ($data as $item) {
    if (is_null($item['parent_id'])) {
        $item['parent_id'] = PHP_INT_SIZE;
    }
    $parent_ids[]  = $item['parent_id'];
}

See result with: print_r($data);.