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Association API

Another way to use many-to-many relations is to use the R::associate() function. This function takes two beans and associates them. To get all beans related to a certain bean you can use its counterpart R::related().


    R::associate( $book, $page );
    R::related( $page, 'book' ); 
    R::relatedOne( $page, 'book'); //just the first bean

To break the association between the two:


    R::unassociate( $book, $page );

To unassociate all related beans:


    R::clearRelations( $book, 'page' );

From version 3.3 on you can use multiple beans with (un)associate, like this: R::associate($wines, $barrels);

Are Related

To find out whether two specific beans are related, use the R::areRelated() function.


    R::areRelated( $husband, $wife );

This function returns TRUE if the two beans have been associated using a many-to-many relation (associate) and FALSE otherwise.

Association and SQL

With the Association API it's possible to include some SQL in your relational query:


    R::related( $album, 'track', ' length > ? ', array($seconds) );

Extended Many-to-many relations are deprecated as of RedBeanPHP 3.4.
As of RedBeanPHP 3.4 you really don't need this functionality anymore. Instead use the intermediate bean notation.

An extended association is a many-to-many association with some extra information.


    R::associate($track,$album,array('sequencenumber'=>$s));

JSON is also allowed:


    R::associate($track,$album,'{"order":"2"}');

Or just a string:


    R::associate($track,$album,'2'); //stored in property 'extra'

To load a association link:


    $keys = R::$extAssocManager->related($album,'track');

Be careful with extended relations

Note that you almost never need extended associations at all. In most cases an intermediate bean is better. For instance, imagine a project bean and a person bean. You want to connect a person to a project so maybe you think:


    R::associate($project,$person);

But then you realize you need to specify a role as well. It's tempting to switch to an extended association now, however this is not a good idea. What you are really looking at is an intermediate bean. Don't try to obscure this bean in a relation. In this case we have to differentiate between a person and a participant.


    $participant->person = $person;
    $participant->role = 'developer';
    $project->ownParticipant[] = $participant;

This approach has several advantages; you can easily add more information to the participant bean:


    $participant->leader = true;

You can model the fact that participants can be represented by multiple persons (for instance if someone gets ill):


    $participant->person = $replace;

...and it's also easy to find out how frequently someone is participating in projects:


    $activities = $person->ownParticipant;

It would be cumbersome hide all this in a link table by using extended associations.

Here is my rule of thumb: if you need to qualify a relationship you probably need to use an intermediate bean.


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