Pagination not getting previous cursor google app engine in php - php

Question

Hi have implement pagination in google app engine
with this code
https://github.com/GoogleCloudPlatform/php-docs-samples/blob/master/datastore/api/src/functions/concepts.php
function cursor_paging(DatastoreClient $datastore, $pageSize, $pageCursor = '')
{
$query = $datastore->query()
->kind('Task')
->limit($pageSize)
->start($pageCursor);
$result = $datastore->runQuery($query);
$nextPageCursor = '';
$entities = [];
/* #var Entity $entity */
foreach ($result as $entity) {
$nextPageCursor = $entity->cursor();
$entities[] = $entity;
}
return array(
'nextPageCursor' => $nextPageCursor,
'entities' => $entities
);
}
geting the next Cursor but did not get the previous cursor form this

Answer 1

Indeed, dealing with the previous cursor is something of a problem - even in other languages, it seems to be the bigger issue, when paginating data. There isn't much data or articles in the internet as well, on how to achieve that.
I will try to explain as much as I can, the possibilities, I believe, are available to you.
As per this other question from the Community here, you can create a new cursor with the information previous page, so you can use it for your pagination. This means that you would have three cursors now: $pageCursor, $nextPageCursor and $previousPageCursor. Using like this, you should be able to maintain the actual data, before setting the one for the next page.
Besides that, there is a reverse method in PHP that might help you, in case you want to count how many pages there will be on your application and put it backwards in the previous cursor. This way, you will have the inverted order, to use in your pagination as well - I still believe that giving a try in the first option, would be the best.
I have found some other useful questions from the Community, that might help you achieve your goal - that I believe are worth taking a look at it as well.
How do appengine cursors work?
App Engine datastore paging - previous page
Let me know if the information helped you!