Question

In the process of learning to use Mongo and PHP, and got stuck with this.
I have a collection in Mongo with the following structure:

array(3){
["timehack"]=>int(..),  
["_id"]=>object..,  
["series"]=>  
array(3){  
    [0]=>int(..),  
    [1]=>int(..),  
    [2]=>int(..)  
}  
}  

I am trying to query the collection so i get all of the samples with first item in “series”, something like:

$cursor = $collection->find();
$cursor->fields(array=>("timehack"=>true, "_id"=>false, "series.0"=>true));
$arr = $cursor->getNext();
var_dump($arr);

The resulting series array is empty. How can I get just the desired index? (I realize that I can get all samples in the series then filter with code, but I would like to know how to accomplish this with a query). Thanks.

Answer 1

In the comments above you have already confirmed that this works with the $slice operator in the shell. So, to give you an example of how $slice works in PHP, I refer you to none other than the PHP tests in the driver itself.

Take a look at line 33 in the tests/MongoCollectionTest2.php file on github:

https://github.com/mongodb/mongo-php-driver/blob/master/tests/MongoCollectionTest2.php

The code goes like this:

$m = new Mongo();
$db = new MongoDB($m, "phpunit");
$this->object = $db->selectCollection('c');
...
...
$results = $this->object->find(array(),array("x" => array('$slice' => 3)))->getNext();

It looks a little convoluted compared to the shell with a lot of casting as an object going on (if I am reading that right), but hopefully enough to get you started 🙂