It's DataMapper to map objects into storages: MySQL or Redis.

Main classes are:
Mapper.php - basic mapper, which can use:
Redis\Gateway.php - gateway to Redis storage
MySQL\Gateway.php - gateway to MySQL

To understand, how it works, read about patterns: Data Mapper and Table Data Gateway

Gateways uses MetaTable to map schema of your table, this schema can be fetched from existing database, or imported by array, or constructed directly in code.