public function array_group_by($arr, $key)
{
$grouped = [];
foreach ($arr as $value) {
$grouped[$value[$key]][] = $value;
}
if (func_num_args() > 2) {
$args = func_get_args();
foreach ($grouped as $key => $value) {
$parms = array_merge([$value], array_slice($args, 2, func_num_args()));
$grouped[$key] = call_user_func_array('array_group_by', $parms);
}
}
return $grouped;
}
