Mixed multi-level order list sort https://blog.shalvah.me/posts/a-mixed-multi-level-order-list-sort-implementation

sort.php

<?php

$orderList = [
  'Jake',
  'Scully' => [
    'pet',
    'friend' => [
      'Michael',
      'Merissa',
    ],
    'Norm',
  ],
  'Amy',
  'Charles',
  'Hitchcock',
];

$items = [
  [ 
    'name' => 'Scully',
    'related' => [
      [ 'name' => 'Norm', 'category' => 'self' ],
      [ 'name' => 'Earl', 'category' => 'friend' ],
      [ 'name' => 'Kelly', 'category' => 'pet' ],
      [ 'name' => 'Michael', 'category' => 'friend' ],
      [ 'name' => 'Merissa', 'category' => 'friend' ],
    ], 
  ],
  [
    'name' => 'Rosa',
    'related' => [],
  ],
  [
    'name' => 'Jake',
    'related' => [
      [ 'name' => 'Franzia', 'category' => 'nemesis' ],
      [ 'name' => 'Doug' ],
    ],
  ],
  [
    'name' => 'Hitchcock',
    'related' => [],
  ],
  [
    'name' => 'Amy',
    'related' => [],
  ],
];


function getTopLevelItemsFromMixedList(array $mixedList): array {
  $topLevels = [];
  foreach ($mixedList as $item => $value) {
    $topLevels[] = is_int($item) ? $value : $item;
  }
  return $topLevels;
}

function sort_by(array $array, callable $sortKeyResolver, ...$sortArgs) {
  $mapped = array_map($sortKeyResolver, $array);
  asort($mapped, ...$sortArgs);
   
  $sorted = [];
  foreach ($mapped as $key => $index) {
    $sorted[] = $array[$key];
  }
   
  return $sorted;
}

$topLevelOrder = getTopLevelItemsFromMixedList($orderList);
$sortKeyResolver = function ($item) use ($topLevelOrder) { 
    $orderListIndex = array_search($item['name'], $topLevelOrder);
    return $orderListIndex === false ? count($topLevelOrder).$item['name'] : $orderListIndex;
};


// First, sort parents
$items = sort_by($items, $sortKeyResolver, SORT_NATURAL);


// Then sort children
foreach ($items as &$item) {
  $children = $item['related'] ?? [];
  
  if(empty($orderList[$item['name']])) {
    // No order was specified for the children, so just sort them as normal
    $item['related'] = sort_by($children, fn ($child) => $child['name'], SORT_NATURAL);
    continue;
  }

  // An order was specified; it can contain children names or categories,
  // so let'sjust  call it the "Level 2" order (L2).
  $l2Order = getTopLevelItemsFromMixedList($orderList[$item['name']]);
  $sortKeyResolver = function ($childItem) use ($l2Order) {
    // First, we check if there's an entry for the item's name
    $indexOfChildInL2Order = array_search($childItem['name'], $l2Order);
    if ($indexOfChildInL2Order !== false) {
      return $indexOfChildInL2Order;
    }

    // Check if there's an entry for the item's category
    $indexOfCategoryInL2Order = array_search($childItem['category'], $l2Order);
    if ($indexOfCategoryInL2Order !== false) {
      // There's an entry for the category! 
      // Now check if there's an entry for the item within the category.
      $orderOfChildrenInCategory = $l2Order[$childItem['category']] ?? [];
      $indexOfChildInCategory = array_search($childItem['name'], $orderOfChildrenInCategory);
      
      return $indexOfChildInCategory === false 
        ? $indexOfCategoryInL2Order.$childItem['name'] 
        : ($indexOfCategoryInL2Order + ($indexOfChildInCategory * 0.1));
    }

    return count($l2Order).$childItem['name'];
  };

  $item['related'] = sort_by($children, $sortKeyResolver, SORT_NATURAL);
}

print_r($items);