Use Result of Aggregation MongoDB in PHP - php

Question

I have this code:
$data = $collection->aggregate(
array(
'$group'=> array(
'_id' => $fn,
'massi' => array(
'$max' => $dnameth_value
)
)
)
);
I execute this query and I want to obtain only MAX Value, and use this in variable.
I tried this code :
$data=$collection->aggregate(array( '$group'=> array('_id'=>$fn,'massi'=>array('$max'=>$dnameth_value))));
var_dump( $data['result'] );
$func = function($value) {
return $value->massi;};
$massi = array_map($func, $data['result']);
var_dump($massi);
Output in the image attach

Answer 1

When you execute the query, the return value of the aggregate() helper method is an array with two elements: ok with a value of double(1) as well as a result element containing an array of all the documents that made it through the whole pipeline.
For instance, if you want to group all the documents by the field my_key and you want to obtain the maximum dnameth_value from that group, and you execute this aggregation operation
<?php
$m = new MongoClient;
$collection = $m->test->collection;
$fn = '$my_key';
$dnameth_value = '$dnameth_value'
$data = $collection->aggregate(
array(
'$group'=> array(
'_id' => $fn,
'massi' => array(
'$max' => $dnameth_value
)
)
)
);
var_dump( $data['result'] );
?>
you should expect the result array from $data['result'] to come in the following form (for example):
…
array (
'_id' => 'value',
'massi' => double(13),
),
array (
'_id' => 'other_value',
'massi' => double(9),
),
array (
'_id' => 'another_value',
'massi' => double(4),
),
…
Note: Because the aggregation framework returns all of its results as one document over the network, the full result is limited to 16MB. There are also memory limits internally, so it is always wise to restrict the data coming through the pipeline with an operator as soon as you can.
So, with your request, you basically would want to map all the massi values from the array into another array variable using array_map():
<?php
$m = new MongoClient;
$collection = $m->test->collection;
$fn = '$my_key';
$dnameth_value = '$dnameth_value'
$data = $collection->aggregate(
array(
'$group'=> array(
'_id' => $fn,
'massi' => array(
'$max' => $dnameth_value
)
)
)
);
var_dump( $data['result'] );
$func = function($value) {
return $value['massi'];
};
$massi = array_map($func, $data['result']);
var_dump($massi);
?>
Now, suppose you are grouping all the documents in the collection then specify an _id value of null to calculate accumulated values for all the input documents as a whole. The resulting array will have one element which you can access by its index:
<?php
$m = new MongoClient;
$collection = $m->test->collection;
$fn = 'null';
$dnameth_value = '$dnameth_value'
$data = $collection->aggregate(
array(
'$group'=> array(
'_id' => $fn,
'massi' => array(
'$max' => $dnameth_value
)
)
)
);
var_dump( $data['result'] );
$massi = $data['result'][0]['massi'];
var_dump($massi);
?>