块数组的值

Question

how do you chunk array like this below?

array(
[0] => array(
    ['id'] => '1',
    ['parent_id'] => ''
)
[1] => array(
    ['id'] => '2',
    ['parent_id'] => ''
)
[2] => array(
    ['id'] => '3',
    ['parent_id'] => '1'
)
[3] => array(
    ['id'] => '3',
    ['parent_id'] => '1'
)
[4] => array(
    ['id'] => '3',
    ['parent_id'] => '2'
)
)

I'd like to group subelements (with specified parent_id) to do a separate foreach.

Answer 1

You can do a simple foreach and rearrange the array.

$result = array();
foreach ($arr as $element) {
  $result[$element['parent_id']][] = $element;
}

http://phpfiddle.org/main/code/3ar-ixg