Finding Documents using MongoCollection::findOne

Finding Documents using MongoCollection::findOne()

To show that the document we inserted in the previous step is stored in the database, we can do a simple MongoCollection::findOne() operation to get a single document from the collection. This method is useful when there is only one document matching the query or you are only interested in one result.


<?php
$connection = new MongoClient();
$collection = $connection->database->collectionName;

$document = $collection->findOne();
var_dump( $document );
?>

Il precedente esempio visualizzerà:

array(6) {
  ["_id"]=>
  object(MongoId)#8 (1) {
    ["$id"]=>
    string(24) "4e2995576803fab768000000"
  }
  ["name"]=>
  string(7) "MongoDB"
  ["type"]=>
  string(8) "database"
  ["count"]=>
  int(1)
  ["info"]=>
  array(2) {
    ["x"]=>
    int(203)
    ["y"]=>
    int(102)
  }
  ["versions"]=>
  array(3) {
    [0]=>
    string(5) "0.9.7"
    [1]=>
    string(5) "0.9.8"
    [2]=>
    string(5) "0.9.9"
  }
}

Note that there is an _id field that has been added automatically to your document. _id is the "primary key" field. If your document does not specify one, the driver will add one automatically.

If you specify your own _id field, it must be unique to the collection. See the example here:


<?php
$connection = new MongoClient();
$db = $connection->database;

$db->foo->insert(array("_id" => 1));
// this will throw an exception
$db->foo->insert(array("_id" => 1));

// this is fine, as it is a different collection
$db->bar->insert(array("_id" => 1));
?>

By default the driver will ensure the server has acknowledged the write before returning. You can optionally turn this behaviour off by passing array("w" => 0) as the second argument. This means that the driver should not wait for the database to acknowledge the write and would not throw the duplicate _id exception.

Finding Documents using MongoCollection::findOne()

See Also