(PECL mongo >=1.3.0)
Perform an aggregation using the aggregation framework
public array MongoCollection::aggregate ( array $pipeline [, array $options ] )
public array MongoCollection::aggregate ( array $op [, array $op [, array $... ]] )
The MongoDB » aggregation framework provides a means to calculate aggregated values without having to use MapReduce. While MapReduce is powerful, it is often more difficult than necess