<?php
$collection->insert(array("task" => "dishes", "do by" => new MongoMaxKey));
$collection->insert(array("task" => "staff meeting", "do by" => new MongoDate(strtotime("+4 days"))));
$cursor = $collection->find()->sort(array("do by" => 1));
?>
The cursor will contain the staff meeting document, then the dishes
document. The dishes document will always be returned last, regardless of
what else is added to the collection (unless other documents are added with
MongoMaxKey in the "do by" field).