Entities, by definition, have an identity, which we can use to save it and get it back from storage again.

Entities are stateful objects that guarantee their consistency and will be persisted somehow.

Repositories are used to save and retrieve domain objects. This post explains how to map entity data to table columns using an ORM, like Doctrine. It also compares the Data Mapper design pattern used with repositories to the Active Record design pattern.

Decoupling infrastructure from core application logic makes understanding and developing the code easier.

How to extract data from associative arrays.