php 多維數組排序

<?php
$arr = array(
    '0' => array(
        'num1' => 3,
        'num2' => 27 
    ),

    '1' => array(
        'num1' => 5,
        'num2' => 50
    ),

    '2' => array(
        'num1' => 4,
        'num2' => 44
    ),

    '3' => array(
        'num1' => 3,
        'num2' => 78
    ) 
);

foreach ( $arr as $key => $row ){
    $num1[$key] = $row ['num1'];
    $num2[$key] = $row ['num2'];
}

array_multisort($num1, SORT_DESC, $num2, SORT_DESC, $arr);

print_r($arr);