Getting started with the Doctrine associations
We will specify Doctrine associations, such as other mapping information, using annotations (other methods such as XML and YAML configuration files are also supported. See Chapter 2, Entities and Mapping Information). Doctrine supports the following association types:
One-To-One: One entity is linked to one entity
Many-To-One: Several entities are linked to one entity (only available for bidirectional associations and always the inverse side of a One-To-Many association)
One-To-Many: One entity is linked to several entities
Many-To-Many: Several entities are linked to several entities
An association can be unidirectional or bidirectional. Unidirectional associations only have an owning side while bidirectional associations have both an owning side and an inverse side. In other words they can be explained as follows:
A unidirectional association can be used in only one way: related entities are retrievable from the main entities. For example, a...
