Как правильно объединить массив?

function mergeAs($key, $arr, $to) {
    if (count($arr) !== count($to)) {
        throw new \InvalidArgumentException ("Arrays must have the same size");
    }
    
    $merged = [];
    foreach ($to as $index=>$element) {
        $element[$key] = $arr[$index];
        $merged[] = $element;
    }
    
    return $merged;
}

$orderIds = ["7", "4", "3", "5", "6", "1"];
$files = [
    [
        'name' => "Screenshot from 2019-01-10 15-04-58.png", 
        'type' => "image/png",
        'tmp_name' => "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a70d8",
        'error' => 0,
        'size' => 249784
    ],
    [
        'name' => "Screenshot from 2019-01-09 16-29-26.png", 
        'type' => "image/png",
        'tmp_name' => "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a7179",
        'error' => 0,
        'size' => 440472
    ],
    [
        'name' => "Screenshot from 2019-01-07 18-10-31.png", 
        'type' => "image/png",
        'tmp_name' => "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a71cb",
        'error' => 0,
        'size' => 175614
    ],
    [
        'name' => "par-de-ruedas-dentadas-dos-tamanos_318-44594.jpg", 
        'type' => "image/jpeg",
        'tmp_name' => "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a721c",
        'error' => 0,
        'size' => 26891
    ],
    [
        'name' => "300614.png", 
        'type' => "image/png",
        'tmp_name' => "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a7264",
        'error' => 0,
        'size' => 11784
    ],
    [
        'name' => "0.jpeg", 
        'type' => "image/jpeg",
        'tmp_name' => "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a72ac",
        'error' => 0,
        'size' => 291469
    ]
];

$files = mergeAs("order", $orderIds, $files);
var_dump($files);

/* Result */
/*
array(6) {
  [0]=>
  array(6) {
    ["name"]=>
    string(39) "Screenshot from 2019-01-10 15-04-58.png"
    ["type"]=>
    string(9) "image/png"
    ["tmp_name"]=>
    string(107) "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a70d8"
    ["error"]=>
    int(0)
    ["size"]=>
    int(249784)
    ["order"]=>
    string(1) "7"
  }
  [1]=>
  array(6) {
    ["name"]=>
    string(39) "Screenshot from 2019-01-09 16-29-26.png"
    ["type"]=>
    string(9) "image/png"
    ["tmp_name"]=>
    string(107) "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a7179"
    ["error"]=>
    int(0)
    ["size"]=>
    int(440472)
    ["order"]=>
    string(1) "4"
  }
  [2]=>
  array(6) {
    ["name"]=>
    string(39) "Screenshot from 2019-01-07 18-10-31.png"
    ["type"]=>
    string(9) "image/png"
    ["tmp_name"]=>
    string(107) "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a71cb"
    ["error"]=>
    int(0)
    ["size"]=>
    int(175614)
    ["order"]=>
    string(1) "3"
  }
  [3]=>
  array(6) {
    ["name"]=>
    string(48) "par-de-ruedas-dentadas-dos-tamanos_318-44594.jpg"
    ["type"]=>
    string(10) "image/jpeg"
    ["tmp_name"]=>
    string(107) "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a721c"
    ["error"]=>
    int(0)
    ["size"]=>
    int(26891)
    ["order"]=>
    string(1) "5"
  }
  [4]=>
  array(6) {
    ["name"]=>
    string(10) "300614.png"
    ["type"]=>
    string(9) "image/png"
    ["tmp_name"]=>
    string(107) "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a7264"
    ["error"]=>
    int(0)
    ["size"]=>
    int(11784)
    ["order"]=>
    string(1) "6"
  }
  [5]=>
  array(6) {
    ["name"]=>
    string(6) "0.jpeg"
    ["type"]=>
    string(10) "image/jpeg"
    ["tmp_name"]=>
    string(107) "/var/www/product/public/website/content/tmp/apartment_images_1927b69a6e00d870384ad6877cc50ece_5c3854e9a72ac"
    ["error"]=>
    int(0)
    ["size"]=>
    int(291469)
    ["order"]=>
    string(1) "1"
  }
} 
*/