PHP 入れ子になった配列並びえ

//order_numで並び替えたいとき。

$array = array(
    array(
        'id'        => 0,
        'order_num' => 'key100-01',
        'title'     => 'ベィスドロップ・フリークス',
        'artist'    => 'かめりあ feat. ななひら'
    ),
    array(
        'id'        => 1,
        'order_num' => 'key001-03',
        'title'     => 'CHRONO DIVER -NORNIR-',
        'artist'    =>  'L.E.D.'
    ),  
    array(
        'id'        => 2,
        'order_num' => 'key001-01',
        'title'     => 'illuminate',
        'artist'    => 'Sota Fujimori'
    ),  
    array(
        'id'        => 3,
        'order_num' => 'key001-04', 
        'title'     => 'YYYYY',
        'artist'    => 'XXXXXX'
    ),  

 
);

foreach ((array) $array as $key => $value) {
    $sort[$key] = $value['order_num'];//ソートしたいキー
}
var_dump($sort);

array_multisort($sort, SORT_ASC, $array);
var_dump($array);