This is a simple PHP script that solves the common problem of folks forgetting to add created_at (MongoDate) to all of their documents. This script will get a list of your collections and loop through them, only updating documents that are missing a created_at property; and these are fixed by pulling the date out of the _id object, and convertin…

add_create_date.php

<?php

/**
 * add_create_date.php by Spacemonkey
 * https://gist.github.com/spacemonkey
 * 
 * Loops through all collections in a mongodb database,
 * finds all documents that are missing a created_at property
 * and extracts it from _id and updates the document.
 * 
 * As this is executed only on documents missing the created_at
 * property, you can run it over and over on the same database.
 **/

echo "ALL RIGHTY THEN! LET'S GET THIS PARTY STARTED.\n\n\n";

// CONFIGURATION
$config_host = 'localhost';       // This is your database host
$config_db = 'database';          // This is your database name

/**
 * You should not need to edit anything below this line.
 **/

$m = new mongoClient("mongodb://$config_host");
$db = $m->selectDB($config_db);

// List of collections
$collections = $db->getCollectionNames();

// Set the query options, only find documents missing created_at property
$options = array(
	'created_at' => array( '$exists' => false )
);

// Loop through collections, adding created_at if missing
foreach($collections AS $collection){
	echo "********************\nWORKING ON: $collection\n";
	$c = $db->$collection->find($options);
	echo "There are " . $c->count() . " documents in this collection without the 'created_at' property.\n";
	foreach($c AS $doc){
		// Get proper MongoId object
		$id = $doc["_id"];
		$mongoid = new MongoId($id);
		// Set created_at property
		$doc['created_at'] = new MongoDate( $mongoid->getTimestamp() );
		// Save the document
		$db->$collection->save($doc);
	}
	echo "\n\n";
}