php: query mongodb embedded documents into an array

Question

I have a database that I need to query and I need to get all of the results from an embedded document into an array so I can store them into variables in php. This is what a record of the mongodb looks like:

{
        "_id" : ObjectId("987654321"),
        "roles" : {
               "988434fe-9ac8-390f-abb4-18e4a0cc83fd" : 9,
               "fc261c0f-7124-3c81-89e8-ecb33771fe4e" : 9
        },
        "groupType" : "PUBLIC_GROUP",
        "name" : "Service Tech Role",
        "type" : "usergroup"
}

I can use the PHP function below to get all of the information from this document except for the embedded document data.

function getPerms()
  {
    $m = new MongoClient ("mongodb://localhost" );
    $db = $m->test;
    $collection = $db->roles;
    $query = array( '_id' => $_SESSION['groupId'] );
    $cursor = $collection->find( $query );
    foreach ($cursor as $document) {
      $_SESSION['object_permissions'] = $document["roles"];
    }
  }

What I need is for the "roles" data to be set in an array, like this:

988434fe-9ac8-390f-abb4-18e4a0cc83fd,9
fc261c0f-7124-3c81-89e8-ecb33771fe4e,9

What needs to be done to throw the embedded document into an array so I can store them as session variables in php?

Kavi Siegel · Accepted Answer · 2015-06-02 22:59:48Z

1

I think your error lies elsewhere, it probably is more about the query returning zero documents, or the roles data being an empty array in the first place, or the roles data not existing and you having undefined index errors suppressed.

Can you prove that you can infact get all of the information from this document except for the embedded document data? Do a var_dump($document) inside the loop.

I suspect your script is likely not even making it into the foreach loop. You may need to check for mongodb query errors, or try modifying or removing the the query as a test.

Side note: You should also be using findOne for this rather than find()

$document = $collection->findOne($query);
$_SESSION['object_permissions'] = $document['roles'];

answered Jun 2, 2015 at 22:59

Kavi Siegel

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1 Comment

Cliff Ennis Over a year ago

Right you are, sir! It was an error elsewhere that was returning no documents. Are there performance implications to using find() instead of findOne(), or is it a best practice to ensure that only 1 document is returned when that's all I'm seeking to return?

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