Converting mongodb node codes to php

my node codes work, but when I want to write it in PHP, it does not work. can you help?

node code mongo sh works without any problems

  db.mevcutlot.aggregate([{$match: {_id: {$ne: null}}}, 
    { $sort: { ederi: -1 } },
    { $group: { _id: '$firmasaf', data: { $push: '$$ROOT' } } },
    { $project: { _id: 0, data: { $arrayElemAt: ["$data", 0] } } },
    { $replaceRoot: { newRoot: "$data" } }])

php code

$pipeline=array(
    array(
        '$match' => array(
            '_id' => ['$ne'=>NULL],
         )
    ),
    array(
        '$sort' => array(
             'ederi'=>  -1,
         )
    ),
    array(
        '$group' => array(
             '_id' => '$firmasaf', 'data'=> ['$push'=> '$$ROOT'],            
         )
    ),
    
    array(
        '$project' => array(
        '_id' => 0, 
        'data' => ['$arrayElemAt'=> ["$data", 0]],
         )
    ),
     array(
        '$replaceRoot' => array(
             'newRoot'=> "$data",        
         )
    ),
    
); 
    $mana = $mevcutlot->aggregate($pipeline)->toArray();
    print_r($mana);

I could not return any results

Solution

First I would suggest to optimize your pipeline:

db.mevcutlot.aggregate([
    { $match: {_id: {$ne: null}}}, 
    { $sort: { ederi: -1 } },
    { $group: { _id: '$firmasaf', data: { $push: '$$ROOT' } } },
    { $project: { _id: 0, data: { $arrayElemAt: ["$data", 0] } } },
    { $replaceRoot: { newRoot: "$data" } }
])

{ $match: {_id: {$ne: null}}} does not make any sense, because _id always exists and is never null. Skip this stage.

Instead of

{ $sort: { ederi: -1 } },
{ $group: { _id: '$firmasaf', data: { $push: '$$ROOT' } } },
{ $project: { _id: 0, data: { $arrayElemAt: ["$data", 0] } } },

you can use

{ $sort: { ederi: -1 } },
{ $group: { _id: '$firmasaf', data: { $first: '$$ROOT' } } },

or even shorter just:

{ $group: { _id: '$firmasaf', data: { $top: { output: '$$ROOT', sortBy: { ederi: -1 } } } } },

It should perform better than your query.

Now, regarding your problem: When you use double-quoted string, then variables are replaced by values, see String interpolation

Because $data variable is most likely empty, '$arrayElemAt'=> ["$data", 0] is substituted to '$arrayElemAt'=> ["", 0] and 'newRoot'=> "$data" becomes 'newRoot'=> "". You should get a warning "Warning: Undefined variable $data in..."

Use single-quotes everywhere or escape the $, e.g. "\$data".