Laravel - 对打乱的数组进行分页

Question

I want to paginate a shuffled array of elements. I know Laravel Paginator expect a Collection. In more details, I want to shuffle a resultset from the database. Therefore I have the following line of code:

$getallFragen = $frage->getAllFragen2()->shuffle()->all();

This line selects all questions and shuffles the collection.

Furthermore I want to shuffle the answers from the questions, which also works correctly. Then I want to paginate the items with one item per page, which also works properly, but I receive duplicate items in the pagination. First I thought, it has to be the collection, but the collection is built correctly and I don´t know, what the problem could be. I could imagine, that my own paginator is not working the way it should. I also create an array, where I store the items, which are allowed in the exam and then make a collection out of the array to make sure, that there are no duplicate entries.

$currentPage = LengthAwarePaginator::resolveCurrentPage();
$itemCollection = collect($pruefung);
$perPage = 1;
$currentPageItems = $itemCollection->slice(($currentPage * $perPage) - $perPage, $perPage)->all();
$paginatedItems = new LengthAwarePaginator($currentPageItems, count($itemCollection), $perPage);

$paginatedItems->setPath($request->url());

return view('pruefungssimulation', ["fragen" => $paginatedItems]);

In the frontend I just use @foreach($fragen as $frage) to get all items out of the collection.

Answer 1

I think the problem is that when you go to the next page, the collection is shuffled again.

An example:

Say you have a collection [1, 2, 3] . When you shuffle this collection, you could get [2, 1, 3] . When you are on the first page, this means you see item 1.

When you go to the next page, the collection is shuffled again. This means the collection could be the same, or could be [1, 3, 2] or [3, 1, 2] . So when you see page 2, the item you see could be item 3, item 2 or item 1 (again).

Solution:

If you want to keep the shuffled order, you have to save this order somewhere so it can be used every time a next/previous page is requested.