.. _php/relations/twinnable_many_many:

Twinnable Many to Many
######################

The ``twinnable_many_many`` relation is the equivalent of the FuelPHP native ``many_many`` relation (moreover, it extends ``many_many``).
The difference is that the link is not made on primary keys but on context common IDs.

If you use the ``twinnable_many_many`` relation, the model and the model linked must implement :doc:`Twinnable behaviour </php/behaviours/twinnable>`.

.. seealso::

    * :doc:`Twinnable behaviour </php/behaviours/twinnable>`
    * :doc:`/php/configuration/software/multi_context`.
    * `FuelPHP native many_many <http://fuelphp.com/docs/packages/orm/relations/many_many.html>`__

Configuration
*************

:key_from:                      The key used for the relation in the current model
:model_to:                      The full class name of the target model. Calculated from alias.
:key_to:                        Calculated from the behaviour Twinnable.
:table_through:                 This is the table that connects the 2 models and has both their common IDs in it.
:key_through_from:              The key that matches the current model's common ID.
:key_through_to:                The key that matches the related model's common ID.
:column_context_from:           Calculated from the behaviour Twinnable.
:column_context_common_id_to:   Calculated from the behaviour Twinnable.
:column_context_to:             Calculated from the behaviour Twinnable.
:column_context_is_main_to:     Calculated from the behaviour Twinnable.