Modeling one-to-one and one-to-many relationships can be done via annotations, YAML, or XML. Using annotations, we can define multiple embedded sub-documents within our document, as shown in the following example:

/** @Document */
class User
{
   // ...
   /** @EmbedMany(targetDocument="Phonenumber") */
   private $phonenumbers = array();
   // ...
}
/** @EmbeddedDocument */
class Phonenumber
{
   // ...
}

Here, a User document embeds many phonenumbers. @EmbedOne() will embed one sub-document to be used for modeling one-to-one relationships.

Referencing is similar to embedding, as shown in the following example:

/** @Document */
class User
{
   // ...
   /**
    * @ReferenceMany(targetDocument="Account")
    */
   private $accounts = array();
   // ...
}
/** @Document */
class Account
{
   // ...
}

@ReferenceMany() and @ReferenceOne() are used to model one-to-many and one-to-one relationships via referencing into a separate collection.