Question

I do this way:

$cursorLocations = $collection->find( array("locationName" => $locationName) )->limit(1);

if ($cursorLocations->count(true) == 1) {
    $idLocations = $cursorLocations->getNext();
    echo $idLocations["_id"];
}

I immediately apologize if this question has been, but read the documentation did not find an answer.

Maybe some other way to get the _id?

Answer 1

in Mongo :

db.collection.find({'field': 'value'}, {'_id' : 1});

in PHP:

$cursorLocations = $collection->find( array("locationName" => $locationName), array('_id' => 1) )->limit(1);

The above code will limit your query to retrieving only the _id field and not the other fields, you would still have to extract the value of that field from the result of the find() function – from the $cursor object, like in:

$_id = $cursorLoactions[`_id`];

There is also a MongoCursor method key() which returns the current _id:

http://www.php.net/manual/en/mongocursor.key.php

So you could do this:

$cursorLocations = $collection->find( array("locationName" => $locationName) )->limit(1);
$_id = $cursorLocations->key();