Mandango is a simple, powerful and ultrafast Object Document Mapper (ODM) for PHP and MongoDB.
See the Benchmark project on my results, and to possibly run them yourself.
Mandago aims to be compatible with the mongo extension versions 1.4.5-1.6.6 on php >= 5.5.0, and the mongofill library. Mandango can also be run on HHVM with mongofill or mongofill-hhvm.