Primary Key Annotation

To define simple primary key mark field with PrimaryKey annotation. To define composite primary key, use this annotation on several fields.

When defining custom primary key it is highly recommended to not define _id field. See this issue.

When inheriting from Document, primary key is set to be _id field, but it is not defined explicitly. Field _id is default primary key in MongoDB, and it is fallback primary key in mangan if there are no other keys are defined.

Example of simple pk:

class MyModel implements AnnotatedInterface
{
    /**
    * @PrimaryKey
    */
    public $myId = '';
}

Example of composite primary key when extending from Document:

class MyModel extends Document
{
    /**
    * @PrimaryKey
    */
    public $code = '';

    /**
    * @PrimaryKey
    */
    public $language = '';
}

Fallback primary key, with _id field.

When not using Document, and no special primary key is required, there should be _id field for default MongoDB key. It will be used as a fallback PK when there is no @PrimaryKey.

It is important to use ObjectId sanitizer on _id:

class MyModel implements AnnotatedInterface
{
    /**
    * @Sanitizer(MongoObjectId)
    */
    public $_id = '';
}