How to sort an inner array in a document? - php

Question

I'm doing "inserts" by $push in an array inside my document, and inside it there is a field date that I want to sort it when I use the find(), but not sorting the "_id". How do I sort by date (ordens.dtOrdem)?
<?php
$mongo = (new MongoDB\Client('mongodb://localhost:27017'))->Carteira;
$collection = $mongo->ativo;
/*First way that I've tried*/
$result1 = $collection->find([].['ordens' => ['sort' => ['dtOrdem' => -1]]]);
/*Second way that I've tried*/
$result2 = $collection->find([],['ordens' => ['each' => ['ordens' => ['sort' => ['dtOrdem' = -1]]]]]);
?>
The field 'ordens.dtOrdem' is no been sorted in descending.

Answer 1

You cannot sort an array during a find(). You have two options:
You can specify a $sort operation during your $push to ensure that your elements are added to the array in sorted order.
You can using aggregation to sort the array on retrieval.
Solutions might look something like the following (some modification may be necessary):
// Sorting on push.
$collection->updateOne(
[...],
[ '$push' => [
'ordens' => [
// You MUST include the $each operator here or this will not work.
'$each' => [
[ 'dtOrdem' => 5 ]
],
// Where the magic happens, sorts in descending order.
'$sort'=> [ 'dtOrdem' => -1 ]
]
]]
);
// Sorting on retrieval.
$collection->aggregate([
[ '$unwind' => '$ordens' ],
[ '$sort' => [
'$ordens.dtOrdem' => -1
]],
[ '$group' => [
'_id' => '$_id',
'ordens' => [
'$push' => '$ordens'
]
]]
]);