Laravel Collection Transform/Map Method Inconsistent Behaviour - php

Question

In my HTML frontend, I have a jQuery DataTable displaying all records fetched via AJAX from the database - a rather pretty straight forward thing. I use the Laravel Collection's ->transform(function($o){ . . . }) to iterate through the collection and return it in an array-esque manner. Just think of the following piece of code in a controller:
$cAllRecords = DatabaseRecord::all();
if(!empty($aData['sFilterIds']))
{
$cAllRecords = $cAllRecords->whereIn('creator', explode(',', $aData['sFilterIds']));
}
return response()->json(['data' => $cAllRecords->transform(function ($oDatabaseRecord) {
/** #var $oDatabaseRecord DatabaseRecord */
$sActionsHtml = 'edit';
$sUrl = route('some.route', ['iDatabaseRecordId' => $oDatabaseRecord->getAttribute('od')]);
return [
$oDatabaseRecord->getAttribute('id'),
$oDatabaseRecord->getAttribute('updated_at')->toDateTimeString(),
$oDatabaseRecord->getAttribute('created_at')->toDateTimeString(),
$sActionsHtml
];
})]);
I'm actually just filtering for records created by certain user IDs (the whereIn() call in line 4. However, the response sent back to the client looks different for different users filtered leading the jQuery table to show 'no records available', as it had received an malformed answer from the server. For one user, the response looks like this:
{
"data":[
[
1,
"2019-05-29 16:44:53",
"2019-05-29 16:44:53",
"<a href=\"#\">edit<\/a>"
]
]
}
This is a correctly formed server response and will show up in the table regularly. Great! Now something that drives me insane - the same code for another user (ID 1, while the first request was for user ID 2) returns this:
{
"data":{
"1":[
3,
"2019-05-29 17:08:49",
"2019-05-29 17:08:49",
"<a href=\"#\">edit<\/a>"
]
}
}
which, pretty obviously, is malformed and is not correctly parsed by the datatable. OK, now combing them two filters and filtering for user ID 1 and 2 will, again, return the response correctly formatted:
{
"data":[
[
1,
"2019-05-29 16:44:53",
"2019-05-29 16:44:53",
"<a href=\"#\">edit<\/a>"
],
[
3,
"2019-05-29 17:08:49",
"2019-05-29 17:08:49",
"<a href=\"#\">edit<\/a>"
]
]
}
I tried a number of things, none of which had worked since it's merely guessing why it could work with one user and not with another. (Things like reversing the order of IDs to be filtered, etc., but I found out that the filtering is not the problem. It MUST be the transform, which behaves inconsistent.)
Any ideas on why this happens and how to tackle it? I mean, it's not the only way to achieve what I'm after, I was using ->each() and array_push for all the time before but wanted to get rid of it for the sake of making use of Laravel's helpers (or possibilites) - the manual iteration and array pushing process worked out seamlessly before, and even other parts of the app work well with the Collection transform over array iteration and pushing. Why doesn't it here?
Update: The ->map() collection method behaves exactly same. Map, as opposed by transform, does not alter the collection itself. However, this should not be a relevant part within this application any way. I really can't understand what's going wrong. Is this possibly Laravel's fault?

Answer 1

Please note that transform method returns a Illuminate\Support\Collection.
It's better that you call all() after the transform to get an array result.
Like this:
...
return response()->json(['data' => $cAllRecords->transform(function ($oDatabaseRecord) {
/** #var $oDatabaseRecord DatabaseRecord */
$sActionsHtml = 'edit';
$sUrl = route('some.route', ['iDatabaseRecordId' => $oDatabaseRecord->getAttribute('od')]);
return [
$oDatabaseRecord->getAttribute('id'),
$oDatabaseRecord->getAttribute('updated_at')->toDateTimeString(),
$oDatabaseRecord->getAttribute('created_at')->toDateTimeString(),
$sActionsHtml
];
})->all()]);

Answer 2

#Cvetan Mihaylov's answer made me look at all the available collection methods (https://laravel.com/docs/5.8/collections#available-methods) and I found ->values() to return the values reindexed. And - that did the trick! :-)
return response()->json(['data' => $cAllRecords->transform(function ($oDatabaseRecord) {
/** #var $oDatabaseRecord DatabaseRecord */
$sActionsHtml = 'edit';
$sUrl = route('some.route', ['iDatabaseRecordId' => $oDatabaseRecord->getAttribute('od')]);
return [
$oDatabaseRecord->getAttribute('id'),
$oDatabaseRecord->getAttribute('updated_at')->toDateTimeString(),
$oDatabaseRecord->getAttribute('created_at')->toDateTimeString(),
$sActionsHtml
];
})->values()]);