Loop through array, and change item details with adding counter - laravel

Question

I am new in Laraver, I am using Eloqunet model... deleteItem function, delete item with offer_in and nbr...When delete item I want to add a new nbr from each item with equal offer_id, starting from 1. I need to define counter = 1, and increase by 1 for every item.. I don't know how to write a for loop, or foreach loop, which pass through selected item, and change 'nbr' with the corresponding value of the counter?
my code is:
public function deleteItem(Request $request, $offer_id, $nbr) {
$item = OfferItem::select('id', 'offer_id', 'nbr', 'product', 'quantity', 'item_price', 'item_tax', 'item_total')
->where('offer_id', $offer_id)
->where('nbr', $nbr)
->first();
$item->delete();
//select new items for offer, after deleting item
$items = OfferItem::select('id', 'offer_id', 'nbr', 'product', 'quantity', 'item_price', 'item_tax', 'item_total')
->where('offer_id', $offer_id)
->get();
//todo
return response()->json($item);
}

Answer 1

Using the Laravel collections, you can just loop the collection and set new count to nbr. Using $count as a reference for the closure, to make the logic work.
$int = 1;
$items->each(function (OfferItem $item) use (&$count) {
$item->nbr = $count;
$item->save();
$count++;
});

Answer 2

You can achieve this purely in SQL like in these examples.
You can achieve what you want using Laravel by:
public function deleteItem(Request $request, $offer_id, $nbr) {
OfferItem::query()
->where('offer_id', $offer_id)
->where('nbr', $nbr)
->delete();
// Select new items for offer, after deleting item
$items = OfferItem::where('offer_id', $offer_id)
->where('nbr', '>', $nbr)
->get()
->sortBy('nbr')
->map(function ($item) use ($nbr) {
$update = [
'id' => $item->id,
'nbr' => $nbr,
];
$nbr++;
return $update;
});
OfferItem::query()->update($items);
return response()->json($item); // It is not clear from your question what you
// are trying to return here. Why would you
// return a deleted item?
}