Get all children for a given parent id in array

Question

I have an array like this:

array(
    array(
        'id' => 1,
        'parent_id' => null
    ),
    array(
        'id' => 2,
        'parent_id' => 1
    ),
    array(
        'id' => 3,
        'parent_id' => 2
    ),
    array(
        'id' => 4,
        'parent_id' => null
    ),
    array(
        'id' => 5,
        'parent_id' => 4
    )
);

How can i find all the childrens of a given parent_id including all grand children? For example the function will return 2,3 for parent_id 1.

Thanks.

Answer 1

// I corrected the array to fit your result 1 => 2,3

    <?php

    $test = array(
    array(
            'id' => 1,
            'parent_id' => null
    ),
    array(
            'id' => 2,
            'parent_id' => 1
    ),
    array(
            'id' => 3,
            'parent_id' => 1
    ),
    array(
            'id' => 4,
            'parent_id' => null
    ),
    array(
            'id' => 5,
            'parent_id' => 4
    )
    );

    // 1_2+3
    $parent_childs = ARRAY();
    foreach ($test AS $index => $child) {
        if (!isset($child['parent_id'])) { continue; }
        $parent_childs[$child['parent_id']][] = $child['id'];
    }


    echo '<pre>';var_dump($parent_childs); echo '</pre>';

    ?>