mongo update attachments metadata

updateFilesMetadata.php

<?php
$mongoDB = new Mongo();
$database = $mongoDB->selectDB("BVS");
$collection = $database->createCollection('fs.files');

$search = array("metadata.formdata.claimid" => "4");
$replace = array('$set'=>array("metadata.formdata.mynewfield" => "wibble")); // note use of single quotes around $set.  This is compulsory
$multiple = array("multiple" => true); // used to update all records that match default is false (update first record only)
$collection->update($search, $replace, $multiple);
?>