(PECL mongo >= 1.0.2)
MongoMinKey is an special type used by the database that compares less than all other possible BSON values. Thus, if a query is sorted by a given field in ascending order, any document with a MongoMinKey as its value will be returned first.
MongoMinKey has no associated fields, methods, or constants. It is merely the "smallest" value that can be represented in the database.
Note: MongoMinKey is used internally by MongoDB for indexing and sharding. There is generally no reason to use this class in an application.
$collection->insert(array("task" => "lunch", "doBy" => new MongoMinKey));
$collection->insert(array("task" => "staff meeting", "doBy" => new MongoDate(strtotime("+4 days"))));
$cursor = $collection->find()->sort(array("doBy" => 1));
The cursor will return the lunch document followed by the staff meeting document. The lunch document will always be returned first, regardless of what else is added to the collection (unless other documents are added with MongoMinKey in their "doBy" field).