Welcome to the Cookbook

The four association types in CakePHP are: hasOne, hasMany, belongsTo, and hasAndBelongsToMany (HABTM).

Relationship	Association Type	Example
one to one	hasOne	A user has one profile.
one to many	hasMany	A user can have multiple recipes.
many to one	belongsTo	Many recipes belong to a user.
many to many	hasAndBelongsToMany	Recipes have, and belong to many tags.

Associations are defined by creating a class variable named after the association you are defining. The class variable can sometimes be as simple as a string, but can be as complete as a multidimensional array used to define association specifics.

<?php

class User extends AppModel {
    var $name = 'User';
    var $hasOne = 'Profile';
    var $hasMany = array(
        'Recipe' => array(
            'className'  => 'Recipe',
            'conditions' => array('Recipe.approved' => '1'),
            'order'      => 'Recipe.created DESC'
        )
    );
}

?>

1. <?php
2. class User extends AppModel {
3. var $name = 'User';
4. var $hasOne = 'Profile';
5. var $hasMany = array(
6. 'Recipe' => array(
7. 'className' => 'Recipe',
8. 'conditions' => array('Recipe.approved' => '1'),
9. 'order' => 'Recipe.created DESC'
10. )
11. );
12. }
13. ?>

In the above example, the first instance of the word 'Recipe' is what is termed an 'Alias'. This is an identifier for the relationship and can be anything you choose. Usually, you will choose the same name as the class that it references. However, aliases must be unique both within a single model and on both sides of a belongsTo/hasMany or a belongsTo/hasOne relationship. Choosing non-unique names for model aliases can cause unexpected behavior.

Cake will automatically create links between associated model objects. So for example in your User model you can access the Recipe model as

$this->Recipe->someFunction();

1. $this->Recipe->someFunction();

Similarly in your controller you can access an associated model simply by following your model associations and without adding it to the $uses array:

$this->User->Recipe->someFunction();

1. $this->User->Recipe->someFunction();

Remember that associations are defined 'one way'. If you define User hasMany Recipe that has no effect on the Recipe Model. You need to define Recipe belongsTo User to be able to access the User model from your Recipe model

Let’s set up a User model with a hasOne relationship to a Profile model.

First, your database tables need to be keyed correctly. For a hasOne relationship to work, one table has to contain a foreign key that points to a record in the other. In this case the profiles table will contain a field called user_id. The basic pattern is:

hasOne: the other model contains the foreign key.

Relation	Schema
Apple hasOne Banana	bananas.apple_id
User hasOne Profile	profiles.user_id
Doctor hasOne Mentor	mentors.doctor_id

The User model file will be saved in /app/models/user.php. To define the ‘User hasOne Profile’ association, add the $hasOne property to the model class. Remember to have a Profile model in /app/models/profile.php, or the association won’t work.

<?php

class User extends AppModel {
    var $name = 'User';                
    var $hasOne = 'Profile';   
}
?>

1. <?php
2. class User extends AppModel {
3. var $name = 'User';
4. var $hasOne = 'Profile';
5. }
6. ?>

There are two ways to describe this relationship in your model files. The simplest method is to set the $hasOne attribute to a string containing the classname of the associated model, as we’ve done above.

If you need more control, you can define your associations using array syntax. For example, you might want to limit the association to include only certain records.

<?php

class User extends AppModel {
    var $name = 'User';          
    var $hasOne = array(
        'Profile' => array(
            'className'    => 'Profile',
            'conditions'   => array('Profile.published' => '1'),
            'dependent'    => true
        )
    );    
}
?>

1. <?php
2. class User extends AppModel {
3. var $name = 'User';
4. var $hasOne = array(
5. 'Profile' => array(
6. 'className' => 'Profile',
7. 'conditions' => array('Profile.published' => '1'),
8. 'dependent' => true
9. )
10. );
11. }
12. ?>

Possible keys for hasOne association arrays include:

• className: the classname of the model being associated to the current model. If you’re defining a ‘User hasOne Profile’ relationship, the className key should equal ‘Profile.’
• foreignKey: the name of the foreign key found in the other model. This is especially handy if you need to define multiple hasOne relationships. The default value for this key is the underscored, singular name of the current model, suffixed with ‘_id’. In the example above it would default to 'user_id'.
• conditions: An SQL fragment used to filter related model records. It’s good practice to use model names in SQL fragments: “Profile.approved = 1” is always better than just “approved = 1.”
• fields: A list of fields to be retrieved when the associated model data is fetched. Returns all fields by default.
• order: An SQL fragment that defines the sorting order for the returned associated rows.
• dependent: When the dependent key is set to true, and the model’s delete() method is called with the cascade parameter set to true, associated model records are also deleted. In this case we set it true so that deleting a User will also delete her associated Profile.

Once this association has been defined, find operations on the User model will also fetch a related Profile record if it exists:

//Sample results from a $this->User->find() call.

Array
(
    [User] => Array
        (
            [id] => 121
            [name] => Gwoo the Kungwoo
            [created] => 2007-05-01 10:31:01
        )
    [Profile] => Array
        (
            [id] => 12
            [user_id] => 121
            [skill] => Baking Cakes
            [created] => 2007-05-01 10:31:01
        )
)

Now that we have Profile data access from the User model, let’s define a belongsTo association in the Profile model in order to get access to related User data. The belongsTo association is a natural complement to the hasOne and hasMany associations: it allows us to see the data from the other direction.

When keying your database tables for a belongsTo relationship, follow this convention:

belongsTo: the current model contains the foreign key.

Relation	Schema
Banana belongsTo Apple	bananas.apple_id
Profile belongsTo User	profiles.user_id
Mentor belongsTo Doctor	mentors.doctor_id

If a model(table) contains a foreign key, it belongsTo the other model(table).

We can define the belongsTo association in our Profile model at /app/models/profile.php using the string syntax as follows:

<?php

class Profile extends AppModel {
    var $name = 'Profile';                
    var $belongsTo = 'User';   
}
?>

1. <?php
2. class Profile extends AppModel {
3. var $name = 'Profile';
4. var $belongsTo = 'User';
5. }
6. ?>

We can also define a more specific relationship using array syntax:

<?php

class Profile extends AppModel {
    var $name = 'Profile';                
    var $belongsTo = array(
        'User' => array(
            'className'    => 'User',
            'foreignKey'    => 'user_id'
        )
    );  
}
?>

1. <?php
2. class Profile extends AppModel {
3. var $name = 'Profile';
4. var $belongsTo = array(
5. 'User' => array(
6. 'className' => 'User',
7. 'foreignKey' => 'user_id'
8. )
9. );
10. }
11. ?>

Possible keys for belongsTo association arrays include:

• className: the classname of the model being associated to the current model. If you’re defining a ‘Profile belongsTo User’ relationship, the className key should equal ‘User.’
• foreignKey: the name of the foreign key found in the current model. This is especially handy if you need to define multiple belongsTo relationships. The default value for this key is the underscored, singular name of the other model, suffixed with ‘_id’.
• conditions: An SQL fragment used to filter related model records. It’s good practice to use model names in SQL fragments: “User.active = 1” is always better than just “active = 1.”
• fields: A list of fields to be retrieved when the associated model data is fetched. Returns all fields by default.
• order: An SQL fragment that defines the sorting order for the returned associated rows.
• counterCache: If set to true the associated Model will automatically increase or decrease the “[singular_model_name]_count” field in the foreign table whenever you do a save() or delete(). If its a string then its the field name to use. The value in the counter field represents the number of related rows.
• counterScope: Optional conditions array to use for updating counter cache field.

Once this association has been defined, find operations on the Profile model will also fetch a related User record if it exists:

//Sample results from a $this->Profile->find() call.

Array
(
   [Profile] => Array
        (
            [id] => 12
            [user_id] => 121
            [skill] => Baking Cakes
            [created] => 2007-05-01 10:31:01
        )    
    [User] => Array
        (
            [id] => 121
            [name] => Gwoo the Kungwoo
            [created] => 2007-05-01 10:31:01
        )
)

Next step: defining a “User hasMany Comment” association. A hasMany association will allow us to fetch a user’s comments when we fetch a User record.

When keying your database tables for a hasMany relationship, follow this convention:

hasMany: the other model contains the foreign key.

Relation	Schema
User hasMany Comment	Comment.user_id
Cake hasMany Virtue	Virtue.cake_id
Product hasMany Option	Option.product_id

We can define the hasMany association in our User model at /app/models/user.php using the string syntax as follows:

<?php

class User extends AppModel {
    var $name = 'User';                
    var $hasMany = 'Comment';   
}
?>

1. <?php
2. class User extends AppModel {
3. var $name = 'User';
4. var $hasMany = 'Comment';
5. }
6. ?>

We can also define a more specific relationship using array syntax:

<?php

class User extends AppModel {
    var $name = 'User';                
    var $hasMany = array(
        'Comment' => array(
            'className'     => 'Comment',
            'foreignKey'    => 'user_id',
            'conditions'    => array('Comment.status' => '1'),
            'order'    => 'Comment.created DESC',
            'limit'        => '5',
            'dependent'=> true
        )
    );  
}
?>

1. <?php
2. class User extends AppModel {
3. var $name = 'User';
4. var $hasMany = array(
5. 'Comment' => array(
6. 'className' => 'Comment',
7. 'foreignKey' => 'user_id',
8. 'conditions' => array('Comment.status' => '1'),
9. 'order' => 'Comment.created DESC',
10. 'limit' => '5',
11. 'dependent'=> true
12. )
13. );
14. }
15. ?>

Possible keys for hasMany association arrays include:

• className: the classname of the model being associated to the current model. If you’re defining a ‘User hasMany Comment’ relationship, the className key should equal ‘Comment.’
• foreignKey: the name of the foreign key found in the other model. This is especially handy if you need to define multiple hasMany relationships. The default value for this key is the underscored, singular name of the actual model, suffixed with ‘_id’.
• conditions: An SQL fragment used to filter related model records. It’s good practice to use model names in SQL fragments: “Comment.status = 1” is always better than just “status = 1.”
• fields: A list of fields to be retrieved when the associated model data is fetched. Returns all fields by default.
• order: An SQL fragment that defines the sorting order for the returned associated rows.
• limit: The maximum number of associated rows you want returned.
• offset: The number of associated rows to skip over (given the current conditions and order) before fetching and associating.
• dependent: When dependent is set to true, recursive model deletion is possible. In this example, Comment records will be deleted when their associated User record has been deleted.
• exclusive: When exclusive is set to true, recursive model deletion does the delete with a deleteAll() call, instead of deleting each entity separately. This greatly improves performance, but may not be ideal for all circumstances.
• finderQuery: A complete SQL query CakePHP can use to fetch associated model records. This should be used in situations that require very custom results.
  
  If a query you're building requires a reference to the associated model ID, use the special {$__cakeID__$} marker in the query. For example, if your Apple model hasMany Orange, the query should look something like this:
  
  

  SELECT Orange.* from oranges as Orange WHERE Orange.apple_id IN ({$__cakeID__$});
  

  1. SELECT Orange.* from oranges as Orange WHERE Orange.apple_id IN ({$__cakeID__$});
  Remember to use IN ({$__cakeID__$}) for hasMany and hasAndBelongsToMany associations as Cake will replace {$__cakeID__$} with a list of ids for these types of associations.
  

Once this association has been defined, find operations on the User model will also fetch related Comment records if they exist:

//Sample results from a $this->User->find() call.

Array
(  
    [User] => Array
        (
            [id] => 121
            [name] => Gwoo the Kungwoo
            [created] => 2007-05-01 10:31:01
        )
    [Comment] => Array
        (
            [0] => Array
                (
                    [id] => 123
                    [user_id] => 121
                    [title] => On Gwoo the Kungwoo
                    [body] => The Kungwooness is not so Gwooish
                    [created] => 2006-05-01 10:31:01
                )
            [1] => Array
                (
                    [id] => 124
                    [user_id] => 121
                    [title] => More on Gwoo
                    [body] => But what of the ‘Nut?
                    [created] => 2006-05-01 10:41:01
                )
        )
)

One thing to remember is that you’ll need a complimentary Comment belongsTo User association in order to get the data from both directions. What we’ve outlined in this section empowers you to get Comment data from the User. Adding the Comment belongsTo User association in the Comment model empowers you to get User data from the Comment model - completing the connection and allowing the flow of information from either model’s perspective.

Alright. At this point, you can already call yourself a CakePHP model associations professional. You're already well versed in the three associations that take up the bulk of object relations.

Let's tackle the final relationship type: hasAndBelongsToMany, or HABTM. This association is used when you have two models that need to be joined up, repeatedly, many times, in many different ways.

The main difference between hasMany and HABTM is that a link between models in HABTM is not exclusive. For example, we're about to join up our Recipe model with a Tag model using HABTM. Attaching the "Italian" tag to my grandma's Gnocci recipe doesn't "use up" the tag. I can also tag my Honey Glazed BBQ Spaghettio's with "Italian" if I want to.

Links between hasMany associated objects are exclusive. If my User hasMany Comments, a comment is only linked to a specific user. It's no longer up for grabs.

Moving on. We'll need to set up an extra table in the database to handle HABTM associations. This new join table's name needs to include the names of both models involved, in alphabetical order, and separated with an underscore ( _ ). The contents of the table should be two fields, each foreign keys (which should be integers) pointing to both of the primary keys of the involved models. To avoid any issues - don't define a combined primary key for these two fields, if your application requires it you can define a unique index. If you plan to add any extra information to this table, it's a good idea to add an additional primary key field (by convention 'id') to make acting on the table as easy as any other model.

HABTM requires a separate join table that includes both model names.

Relation	Schema (HABTM table in bold)
Recipe HABTM Tag	recipes_tags.id, recipes_tags.recipe_id, recipes_tags.tag_id
Cake HABTM Fan	cakes_fans.id, cakes_fans.cake_id, cakes_fans.fan_id
Foo HABTM Bar	bars_foos.id, bars_foos.foo_id, bars_foos.bar_id

Table names are by convention in alphabetical order.

Make sure primary keys in tables cakes and recipes have "id" fields as assumed by convention. If they're different than assumed, it has to be changed in model

Once this new table has been created, we can define the HABTM association in the model files. We're gonna skip straight to the array syntax this time:

<?php

class Recipe extends AppModel {
    var $name = 'Recipe';   
    var $hasAndBelongsToMany = array(
        'Tag' =>
            array(
                'className'              => 'Tag',
                'joinTable'              => 'recipes_tags',
                'foreignKey'             => 'recipe_id',
                'associationForeignKey'  => 'tag_id',
                'unique'                 => true,
                'conditions'             => '',
                'fields'                 => '',
                'order'                  => '',
                'limit'                  => '',
                'offset'                 => '',
                'finderQuery'            => '',
                'deleteQuery'            => '',
                'insertQuery'            => ''
            )
    );
}
?>

1. <?php
2. class Recipe extends AppModel {
3. var $name = 'Recipe';
4. var $hasAndBelongsToMany = array(
5. 'Tag' =>
6. array(
7. 'className' => 'Tag',
8. 'joinTable' => 'recipes_tags',
9. 'foreignKey' => 'recipe_id',
10. 'associationForeignKey' => 'tag_id',
11. 'unique' => true,
12. 'conditions' => '',
13. 'fields' => '',
14. 'order' => '',
15. 'limit' => '',
16. 'offset' => '',
17. 'finderQuery' => '',
18. 'deleteQuery' => '',
19. 'insertQuery' => ''
20. )
21. );
22. }
23. ?>

Possible keys for HABTM association arrays include:

• className: the classname of the model being associated to the current model. If you're defining a ‘Recipe HABTM Tag' relationship, the className key should equal ‘Tag.'
• joinTable: The name of the join table used in this association (if the current table doesn't adhere to the naming convention for HABTM join tables).
• with: Defines the name of the model for the join table. By default CakePHP will auto-create a model for you. Using the example above it would be called RecipesTag. By using this key you can override this default name. The join table model can be used just like any "regular" model to access the join table directly.
• foreignKey: the name of the foreign key found in the current model. This is especially handy if you need to define multiple HABTM relationships. The default value for this key is the underscored, singular name of the current model, suffixed with ‘_id'.
• associationForeignKey: the name of the foreign key found in the other model. This is especially handy if you need to define multiple HABTM relationships. The default value for this key is the underscored, singular name of the other model, suffixed with ‘_id'.
• unique: If true (default value) cake will first delete existing relationship records in the foreign keys table before inserting new ones, when updating a record. So existing associations need to be passed again when updating.
• conditions: An SQL fragment used to filter related model records. It's good practice to use model names in SQL fragments: "Comment.status = 1" is always better than just "status = 1."
• fields: A list of fields to be retrieved when the associated model data is fetched. Returns all fields by default.
• order: An SQL fragment that defines the sorting order for the returned associated rows.
• limit: The maximum number of associated rows you want returned.
• offset: The number of associated rows to skip over (given the current conditions and order) before fetching and associating.
• finderQuery, deleteQuery, insertQuery: A complete SQL query CakePHP can use to fetch, delete, or create new associated model records. This should be used in situations that require very custom results.

Once this association has been defined, find operations on the Recipe model will also fetch related Tag records if they exist:

//Sample results from a $this->Recipe->find() call.

Array
(  
    [Recipe] => Array
        (
            [id] => 2745
            [name] => Chocolate Frosted Sugar Bombs
            [created] => 2007-05-01 10:31:01
            [user_id] => 2346
        )
    [Tag] => Array
        (
            [0] => Array
                (
                    [id] => 123
                    [name] => Breakfast
                )
           [1] => Array
                (
                    [id] => 124
                    [name] => Dessert
                )
           [2] => Array
                (
                    [id] => 125
                    [name] => Heart Disease
                )
        )
)

Remember to define a HABTM association in the Tag model if you'd like to fetch Recipe data when using the Tag model.

It is also possible to execute custom find queries based on HABTM relationships. Consider the following examples:

Assuming the same structure in the above example (Recipe HABTM Tag), let's say we want to fetch all Recipes with the tag 'Dessert', one potential (wrong) way to achieve this would be to apply a condition to the association itself:

$this->Recipe->bindModel(array(
	'hasAndBelongsToMany' => array(
		'Tag' => array('conditions'=>array('Tag.name'=>'Dessert'))
)));
$this->Recipe->find('all');

1. $this->Recipe->bindModel(array(
2. 'hasAndBelongsToMany' => array(
3. 'Tag' => array('conditions'=>array('Tag.name'=>'Dessert'))
4. )));
5. $this->Recipe->find('all');

//Data Returned
Array
(  
    0 => Array
        {
        [Recipe] => Array
            (
                [id] => 2745
                [name] => Chocolate Frosted Sugar Bombs
                [created] => 2007-05-01 10:31:01
                [user_id] => 2346
            )
        [Tag] => Array
            (
               [0] => Array
                    (
                        [id] => 124
                        [name] => Dessert
                    )
            )
    )
    1 => Array
        {
        [Recipe] => Array
            (
                [id] => 2745
                [name] => Crab Cakes
                [created] => 2008-05-01 10:31:01
                [user_id] => 2349
            )
        [Tag] => Array
            (
            }
        }
}

Notice that this example returns ALL recipes but only the "Dessert" tags. To properly achieve our goal, there are a number of ways to do it. One option is to search the Tag model (instead of Recipe), which will also give us all of the associated Recipes.

$this->Recipe->Tag->find('all', array('conditions'=>array('Tag.name'=>'Dessert')));

1. $this->Recipe->Tag->find('all', array('conditions'=>array('Tag.name'=>'Dessert')));

We could also use the join table model (which CakePHP provides for us), to search for a given ID.

$this->Recipe->bindModel(array('hasOne' => array('RecipesTag')));
$this->Recipe->find('all', array(
		'fields' => array('Recipe.*'),
		'conditions'=>array('RecipesTag.tag_id'=>124) // id of Dessert
));

1. $this->Recipe->bindModel(array('hasOne' => array('RecipesTag')));
2. $this->Recipe->find('all', array(
3. 'fields' => array('Recipe.*'),
4. 'conditions'=>array('RecipesTag.tag_id'=>124) // id of Dessert
5. ));

It's also possible to create an exotic association for the purpose of creating as many joins as necessary to allow filtering, for example:

$this->Recipe->bindModel(array(
	'hasOne' => array(
		'RecipesTag',
		'FilterTag' => array(
			'className' => 'Tag',
			'foreignKey' => false,
			'conditions' => array('FilterTag.id = RecipesTag.tag_id')
))));
$this->Recipe->find('all', array(
		'fields' => array('Recipe.*'),
		'conditions'=>array('FilterTag.name'=>'Dessert')
));

1. $this->Recipe->bindModel(array(
2. 'hasOne' => array(
3. 'RecipesTag',
4. 'FilterTag' => array(
5. 'className' => 'Tag',
6. 'foreignKey' => false,
7. 'conditions' => array('FilterTag.id = RecipesTag.tag_id')
8. ))));
9. $this->Recipe->find('all', array(
10. 'fields' => array('Recipe.*'),
11. 'conditions'=>array('FilterTag.name'=>'Dessert')
12. ));

Both of which will return the following data:

//Data Returned
Array
(  
    0 => Array
        {
        [Recipe] => Array
            (
                [id] => 2745
                [name] => Chocolate Frosted Sugar Bombs
                [created] => 2007-05-01 10:31:01
                [user_id] => 2346
            )
    [Tag] => Array
        (
            [0] => Array
                (
                    [id] => 123
                    [name] => Breakfast
                )
           [1] => Array
                (
                    [id] => 124
                    [name] => Dessert
                )
           [2] => Array
                (
                    [id] => 125
                    [name] => Heart Disease
                )
        )
}

The same binding trick can be used to easily paginate your HABTM models. Just one word of caution: since paginate requires two queries (one to count the records and one to get the actual data), be sure to supply the false parameter to your bindModel(); which essentially tells CakePHP to keep the binding persistent over multiple queries, rather than just one as in the default behavior. Please refer to the API for more details.

For more information on saving HABTM objects see Saving Related Model Data (HABTM)

For more information on binding model associations on the fly see Creating and destroying associations on the fly

Mix and match techniques to achieve your specific objective.

Sometimes it becomes necessary to create and destroy model associations on the fly. This may be for any number of reasons:

• You want to reduce the amount of associated data fetched, but all your associations are on the first level of recursion.
• You want to change the way an association is defined in order to sort or filter associated data.

This association creation and destruction is done using the CakePHP model bindModel() and unbindModel() methods. (There is also a very helpful behavior called "Containable", please refer to manual section about Built-in behaviors for more information). Let's set up a few models so we can see how bindModel() and unbindModel() work. We'll start with two models:

<?php

class Leader extends AppModel {
    var $name = 'Leader';
 
    var $hasMany = array(
        'Follower' => array(
            'className' => 'Follower',
            'order'     => 'Follower.rank'
        )
    );
}

?>

<?php

class Follower extends AppModel {
    var $name = 'Follower';
}

?>

1. <?php
2. class Leader extends AppModel {
3. var $name = 'Leader';
5. var $hasMany = array(
6. 'Follower' => array(
7. 'className' => 'Follower',
8. 'order' => 'Follower.rank'
9. )
10. );
11. }
12. ?>
13.  
14. <?php
15. class Follower extends AppModel {
16. var $name = 'Follower';
17. }
18. ?>

Now, in the LeadersController, we can use the find() method in the Leader model to fetch a Leader and its associated followers. As you can see above, the association array in the Leader model defines a "Leader hasMany Followers" relationship. For demonstration purposes, let's use unbindModel() to remove that association in a controller action.

function someAction() {
    // This fetches Leaders, and their associated Followers
    $this->Leader->find('all');
  
    // Let's remove the hasMany...
    $this->Leader->unbindModel(
        array('hasMany' => array('Follower'))
    );
  
    // Now using a find function will return 
    // Leaders, with no Followers
    $this->Leader->find('all');
  
    // NOTE: unbindModel only affects the very next 
    // find function. An additional find call will use 
    // the configured association information.
  
    // We've already used find('all') after unbindModel(), 
    // so this will fetch Leaders with associated 
    // Followers once again...
    $this->Leader->find('all');
}

1. function someAction() {
2. // This fetches Leaders, and their associated Followers
3. $this->Leader->find('all');
5. // Let's remove the hasMany...
6. $this->Leader->unbindModel(
7. array('hasMany' => array('Follower'))
8. );
10. // Now using a find function will return
11. // Leaders, with no Followers
12. $this->Leader->find('all');
14. // NOTE: unbindModel only affects the very next
15. // find function. An additional find call will use
16. // the configured association information.
18. // We've already used find('all') after unbindModel(),
19. // so this will fetch Leaders with associated
20. // Followers once again...
21. $this->Leader->find('all');
22. }

Removing or adding associations using bind- and unbindModel() only works for the next model operation only unless the second parameter has been set to false. If the second parameter has been set to false, the bind remains in place for the remainder of the request.

Here’s the basic usage pattern for unbindModel():

$this->Model->unbindModel(
    array('associationType' => array('associatedModelClassName'))
);

1. $this->Model->unbindModel(
2. array('associationType' => array('associatedModelClassName'))
3. );

Now that we've successfully removed an association on the fly, let's add one. Our as-of-yet unprincipled Leader needs some associated Principles. The model file for our Principle model is bare, except for the var $name statement. Let's associate some Principles to our Leader on the fly (but remember–only for just the following find operation). This function appears in the LeadersController:

function anotherAction() {
    // There is no Leader hasMany Principles in 
    // the leader.php model file, so a find here, 
    // only fetches Leaders.
    $this->Leader->find('all');
 
    // Let's use bindModel() to add a new association 
    // to the Leader model:
    $this->Leader->bindModel(
        array('hasMany' => array(
                'Principle' => array(
                    'className' => 'Principle'
                )
            )
        )
    );
 
    // Now that we're associated correctly, 
    // we can use a single find function to fetch 
    // Leaders with their associated principles:
    $this->Leader->find('all');
}

1. function anotherAction() {
2. // There is no Leader hasMany Principles in
3. // the leader.php model file, so a find here,
4. // only fetches Leaders.
5. $this->Leader->find('all');
7. // Let's use bindModel() to add a new association
8. // to the Leader model:
9. $this->Leader->bindModel(
10. array('hasMany' => array(
11. 'Principle' => array(
12. 'className' => 'Principle'
13. )
14. )
15. )
16. );
18. // Now that we're associated correctly,
19. // we can use a single find function to fetch
20. // Leaders with their associated principles:
21. $this->Leader->find('all');
22. }

There you have it. The basic usage for bindModel() is the encapsulation of a normal association array inside an array whose key is named after the type of association you are trying to create:

$this->Model->bindModel(
        array('associationName' => array(
                'associatedModelClassName' => array(
                    // normal association keys go here...
                )
            )
        )
    );

1. $this->Model->bindModel(
2. array('associationName' => array(
3. 'associatedModelClassName' => array(
4. // normal association keys go here...
5. )
6. )
7. )
8. );

Even though the newly bound model doesn't need any sort of association definition in its model file, it will still need to be correctly keyed in order for the new association to work properly.

There are cases where a Model has more than one relation to another Model. For example you might have a Message model that has two relations to the User model. One relation to the user that sends a message, and a second to the user that receives the message. The messages table will have a field user_id, but also a field recipient_id. Now your Message model can look something like:

<?php
class Message extends AppModel {
    var $name = 'Message';
    var $belongsTo = array(
        'Sender' => array(
            'className' => 'User',
            'foreignKey' => 'user_id'
        ),
        'Recipient' => array(
            'className' => 'User',
            'foreignKey' => 'recipient_id'
        )
    );
}
?>

1. <?php
2. class Message extends AppModel {
3. var $name = 'Message';
4. var $belongsTo = array(
5. 'Sender' => array(
6. 'className' => 'User',
7. 'foreignKey' => 'user_id'
8. ),
9. 'Recipient' => array(
10. 'className' => 'User',
11. 'foreignKey' => 'recipient_id'
12. )
13. );
14. }
15. ?>

Recipient is an alias for the User model. Now let's see what the User model would look like.

<?php
class User extends AppModel {
    var $name = 'User';
    var $hasMany = array(
        'MessageSent' => array(
            'className' => 'Message',
            'foreignKey' => 'user_id'
        ),
        'MessageReceived' => array(
            'className' => 'Message',
            'foreignKey' => 'recipient_id'
        )
    );
}
?>

1. <?php
2. class User extends AppModel {
3. var $name = 'User';
4. var $hasMany = array(
5. 'MessageSent' => array(
6. 'className' => 'Message',
7. 'foreignKey' => 'user_id'
8. ),
9. 'MessageReceived' => array(
10. 'className' => 'Message',
11. 'foreignKey' => 'recipient_id'
12. )
13. );
14. }
15. ?>

In SQL you can combine related tables using the JOIN statement. This allows you to perform complex searches across multiples tables (i.e: search posts given several tags).

In CakePHP some associations (belongsTo and hasOne) performs automatic joins to retrieve data, so you can issue queries to retrieve models based on data in the related one.

But this is not the case with hasMany and hasAndBelongsToMany associations. Here is where forcing joins comes to the rescue. You only have to define the necessary joins to combine tables and get the desired results for your query.

To force a join between tables you need to use the "modern" syntax for Model::find(), adding a 'joins' key to the $options array. For example:

$options['joins'] = array(
    array(
        'table' => 'channels',
        'alias' => 'Channel',
        'type' => 'LEFT',
        'conditions' => array(
            'Channel.id = Item.channel_id',
        )
    )
);

$Item->find('all', $options);

1. $options['joins'] = array(
2. array(
3. 'table' => 'channels',
4. 'alias' => 'Channel',
5. 'type' => 'LEFT',
6. 'conditions' => array(
7. 'Channel.id = Item.channel_id',
8. )
9. )
10. );
11. $Item->find('all', $options);

Note that the 'join' arrays are not keyed.

In the above example, a model called Item is left joined to the channels table. You can alias the table with the model name, so the retrieved data complies with the CakePHP data structure.

The keys that define the join are the following:

• table: The table for the join.
• alias: An alias to the table. The name of the model associated with the table is the best bet.
• type: The type of join: inner, left or right.
• conditions: The conditions to perform the join.

With joins, you could add conditions based on related model fields:

$options['joins'] = array(
    array('table' => 'channels',
        'alias' => 'Channel',
        'type' => 'LEFT',
        'conditions' => array(
            'Channel.id = Item.channel_id',
        )
    )
);

$options['conditions'] = array(
	'Channel.private' => 1
);

$pirvateItems = $Item->find('all', $options);

1. $options['joins'] = array(
2. array('table' => 'channels',
3. 'alias' => 'Channel',
4. 'type' => 'LEFT',
5. 'conditions' => array(
6. 'Channel.id = Item.channel_id',
7. )
8. )
9. );
10. $options['conditions'] = array(
11. 'Channel.private' => 1
12. );
13. $pirvateItems = $Item->find('all', $options);

You could perform several joins as needed in hasBelongsToMany:

Suppose a Book hasAndBelongsToMany Tag association. This relation uses a books_tags table as join table, so you need to join the books table to the books_tags table, and this with the tags table:

$options['joins'] = array(
	array('table' => 'books_tags',
		'alias' => 'BooksTag',
		'type' => 'inner',
		'conditions' => array(
			'Books.id = BooksTag.book_id'
		)
	),
	array('table' => 'tags',
		'alias' => 'Tag',
		'type' => 'inner',
		'conditions' => array(
			'BooksTag.tag_id = Tag.id'
		)
	)
);

$options['conditions'] = array(
	'Tag.tag' => 'Novel'
);

$books = $Book->find('all', $options);

1. $options['joins'] = array(
2. array('table' => 'books_tags',
3. 'alias' => 'BooksTag',
4. 'type' => 'inner',
5. 'conditions' => array(
6. 'Books.id = BooksTag.book_id'
7. )
8. ),
9. array('table' => 'tags',
10. 'alias' => 'Tag',
11. 'type' => 'inner',
12. 'conditions' => array(
13. 'BooksTag.tag_id = Tag.id'
14. )
15. )
16. );
17. $options['conditions'] = array(
18. 'Tag.tag' => 'Novel'
19. );
20. $books = $Book->find('all', $options);

Using joins with Containable behavior could lead to some SQL errors (duplicate tables), so you need to use the joins method as an alternative for Containable if your main goal is to perform searches based on related data. Containable is best suited to restricting the amount of related data brought by a find statement.