Models¶

Data Type Associations by Database¶

Every RDBMS defines data types in slightly different ways. Within the datasource class for each database system, CakePHP maps those types to something it recognizes and creates a unified interface, no matter which database system you need to run on.

This breakdown describes how each one is mapped.

Titles¶

An object, in the physical sense, often has a name or a title that refers to it. A person has a name like John or Mac or Buddy. A blog post has a title. A category has a name.

By specifying a title or name field, CakePHP will automatically use this label in various circumstances:

• Scaffolding — page titles, fieldset labels

• Lists — normally used for <select> drop-downs

• TreeBehavior — reordering, tree views

If you have a title and name field in your table, the title will be used.

If you want to use something other than the convention set var $displayField = 'some_field';. Only one field can be set here.

created and modified¶

By defining a created or modified field in your database table as datetime fields, CakePHP will recognize those fields and populate them automatically whenever a record is created or saved to the database (unless the data being saved already contains a value for these fields).

The created and modified fields will be set to the current date and time when the record is initially added. The modified field will be updated with the current date and time whenever the existing record is saved.

Note: A field named updated will exhibit the same behavior as modified. These fields need to be datetime fields with the default value set to NULL to be recognized by CakePHP.

If you have updated, created or modified data in your $this->data (e.g. from a Model::read or Model::set) before a Model::save() then the values will be taken from $this->data and not automagically updated.

Either use unset($this->data['Model']['modified']), etc. Alternatively you can override the Model::save() to always do it for you:-

class AppModel extends Model {
//
//
    function save($data = null, $validate = true, $fieldList = array()) {

        //clear modified field value before each save
        if (isset($this->data) && isset($this->data[$this->name]))
            unset($this->data[$this->name]['modified']);
        if (isset($data) && isset($data[$this->name]))
            unset($data[$this->name]['modified']);

        return parent::save($data, $validate, $fieldList);
    }
//
//
}

Using UUIDs as Primary Keys¶

Primary keys are normally defined as INT fields. The database will automatically increment the field, starting at 1, for each new record that gets added. Alternatively, if you specify your primary key as a CHAR(36) or BINARY(36), CakePHP will automatically generate UUIDs when new records are created.

A UUID is a 32 byte string separated by four hyphens, for a total of 36 characters. For example:

550e8400-e29b-41d4-a716-446655440000

UUIDs are designed to be unique, not only within a single table, but also across tables and databases. If you require a field to remain unique across systems then UUIDs are a great approach.

find¶

find($type, $params)

Find is the multifunctional workhorse of all model data-retrieval functions. $type can be either 'all', 'first', 'count', 'list', 'neighbors' or 'threaded'. The default find type is 'first'. Keep in mind that $type is case sensitive. Using a upper case character (for example 'All') will not produce the expected results.

$params is used to pass all parameters to the various finds, and has the following possible keys by default - all of which are optional:

array(
    'conditions' => array('Model.field' => $thisValue), //array of conditions
    'recursive' => 1, //int
    'fields' => array('Model.field1', 'DISTINCT Model.field2'), //array of field names
    'order' => array('Model.created', 'Model.field3 DESC'), //string or array defining order
    'group' => array('Model.field'), //fields to GROUP BY
    'limit' => n, //int
    'page' => n, //int
    'offset'=>n, //int
    'callbacks' => true //other possible values are false, 'before', 'after'
)

It’s also possible to add and use other parameters, as is made use of by some find types, behaviors and of course possible with your own model methods

More information about model callbacks is available Models

function some_function() {
   ...
   $this->Article->order = null; // resetting if it's set
   $semiRandomArticle = $this->Article->find();
   $this->Article->order = 'Article.created DESC'; // simulating the model having a default order
   $lastCreated = $this->Article->find();
   $alsoLastCreated = $this->Article->find('first', array('order' => array('Article.created DESC')));
   $specificallyThisOne = $this->Article->find('first', array('conditions' => array('Article.id' => 1)));
   ...
}

Array
(
    [ModelName] => Array
        (
            [id] => 83
            [field1] => value1
            [field2] => value2
            [field3] => value3
        )

    [AssociatedModelName] => Array
        (
            [id] => 1
            [field1] => value1
            [field2] => value2
            [field3] => value3
        )
)

function some_function() {
   ...
   $total = $this->Article->find('count');
   $pending = $this->Article->find('count', array('conditions' => array('Article.status' => 'pending')));
   $authors = $this->Article->User->find('count');
   $publishedAuthors = $this->Article->find('count', array(
      'fields' => 'DISTINCT Article.user_id',
      'conditions' => array('Article.status !=' => 'pending')
   ));
   ...
}

function some_function() {
   ...
   $allArticles = $this->Article->find('all');
   $pending = $this->Article->find('all', array('conditions' => array('Article.status' => 'pending')));
   $allAuthors = $this->Article->User->find('all');
   $allPublishedAuthors = $this->Article->User->find('all', array('conditions' => array('Article.status !=' => 'pending')));
   ...
}

Array
(
    [0] => Array
        (
            [ModelName] => Array
                (
                    [id] => 83
                    [field1] => value1
                    [field2] => value2
                    [field3] => value3
                )

            [AssociatedModelName] => Array
                (
                    [id] => 1
                    [field1] => value1
                    [field2] => value2
                    [field3] => value3
                )

        )
)

function some_function() {
   ...
    $allArticles = $this->Article->find('list');
    $pending = $this->Article->find('list', array(
        'conditions' => array('Article.status' => 'pending')
    ));
    $allAuthors = $this->Article->User->find('list');
    $allPublishedAuthors = $this->Article->find('list', array(
        'fields' => array('User.id', 'User.name'),
        'conditions' => array('Article.status !=' => 'pending'),
        'recursive' => 0
    ));
   ...
}

Array
(
    //[id] => 'displayValue',
    [1] => 'displayValue1',
    [2] => 'displayValue2',
    [4] => 'displayValue4',
    [5] => 'displayValue5',
    [6] => 'displayValue6',
    [3] => 'displayValue3',
)

function some_function() {
   ...
   $justusernames = $this->Article->User->find('list', array('fields' => array('User.username')));
   $usernameMap = $this->Article->User->find('list', array('fields' => array('User.username', 'User.first_name')));
   $usernameGroups = $this->Article->User->find('list', array('fields' => array('User.username', 'User.first_name', 'User.group')));
   ...
}

$justusernames = Array
(
    //[id] => 'username',
    [213] => 'AD7six',
    [25] => '_psychic_',
    [1] => 'PHPNut',
    [2] => 'gwoo',
    [400] => 'jperras',
)

$usernameMap = Array
(
    //[username] => 'firstname',
    ['AD7six'] => 'Andy',
    ['_psychic_'] => 'John',
    ['PHPNut'] => 'Larry',
    ['gwoo'] => 'Gwoo',
    ['jperras'] => 'Joël',
)

$usernameGroups = Array
(
    ['User'] => Array
        (
        ['PHPNut'] => 'Larry',
        ['gwoo'] => 'Gwoo',
        )

    ['Admin'] => Array
        (
        ['_psychic_'] => 'John',
        ['AD7six'] => 'Andy',
        ['jperras'] => 'Joël',
        )

)

function some_function() {
   ...
   $allCategories = $this->Category->find('threaded');
   $aCategory = $this->Category->find('first', array('conditions' => array('parent_id' => 42))); // not the root
   $someCategories = $this->Category->find('threaded', array(
    'conditions' => array(
        'Article.lft >=' => $aCategory['Category']['lft'],
        'Article.rght <=' => $aCategory['Category']['rght']
    )
   ));
   ...
}

Array
(
    [0] => Array
        (
            [ModelName] => Array
                (
                    [id] => 83
                    [parent_id] => null
                    [field1] => value1
                    [field2] => value2
                    [field3] => value3
                )

            [AssociatedModelName] => Array
                (
                    [id] => 1
                    [field1] => value1
                    [field2] => value2
                    [field3] => value3
                )
            [children] => Array
                (
            [0] => Array
            (
                [ModelName] => Array
                (
                    [id] => 42
                            [parent_id] => 83
                    [field1] => value1
                    [field2] => value2
                    [field3] => value3
                )

                [AssociatedModelName] => Array
                (
                    [id] => 2
                    [field1] => value1
                    [field2] => value2
                    [field3] => value3
                )
                    [children] => Array
                (
                )
                    )
            ...
                )
        )
)

function some_function() {
   $neighbors = $this->Article->find('neighbors', array('field' => 'id', 'value' => 3));
}

Array
(
    [prev] => Array
        (
            [ModelName] => Array
                (
                    [id] => 2
                    [field1] => value1
                    [field2] => value2
                    ...
                )
            [AssociatedModelName] => Array
                (
                    [id] => 151
                    [field1] => value1
                    [field2] => value2
                    ...
                )
        )
    [next] => Array
        (
            [ModelName] => Array
                (
                    [id] => 4
                    [field1] => value1
                    [field2] => value2
                    ...
                )
            [AssociatedModelName] => Array
                (
                    [id] => 122
                    [field1] => value1
                    [field2] => value2
                    ...
                )
        )
)

findAllBy¶

findAllBy<fieldName>(string $value, array $fields, array $order, int $limit, int $page, int $recursive)

These magic functions can be used as a shortcut to search your tables by a certain field. Just add the name of the field (in CamelCase format) to the end of these functions, and supply the criteria for that field as the first parameter.

PHP4 users have to use this function a little differently due to some case-insensitivity in PHP4:

The returned result is an array formatted just as it would be from findAll().

findBy¶

findBy<fieldName>(string $value);

The findBy magic functions also accept some optional parameters:

findBy<fieldName>(string $value[, mixed $fields[, mixed $order]]);

These magic functions can be used as a shortcut to search your tables by a certain field. Just add the name of the field (in CamelCase format) to the end of these functions, and supply the criteria for that field as the first parameter.

PHP4 users have to use this function a little differently due to some case-insensitivity in PHP4:

findBy() functions like find(‘first’,…), while findAllBy() functions like find(‘all’,…).

In either case, the returned result is an array formatted just as it would be from find() or findAll(), respectively.

query¶

query(string $query)

SQL calls that you can’t or don’t want to make via other model methods (this should only rarely be necessary) can be made using the model’s query() method.

If you’re ever using this method in your application, be sure to check out CakePHP’s Data Sanitization, which aids in cleaning up user-provided data from injection and cross-site scripting attacks.

query() does not honour $Model->cachequeries as its functionality is inherently disjoint from that of the calling model. To avoid caching calls to query, supply a second argument of false, ie: query($query, $cachequeries = false)

query() uses the table name in the query as the array key for the returned data, rather than the model name. For example,

$this->Picture->query("SELECT * FROM pictures LIMIT 2;");

might return

Array
(
    [0] => Array
        (
            [pictures] => Array
                (
                    [id] => 1304
                    [user_id] => 759
                )
        )

    [1] => Array
        (
            [pictures] => Array
                (
                    [id] => 1305
                    [user_id] => 759
                )
        )
)

To use the model name as the array key, and get a result consistent with that returned by the Find methods, the query can be rewritten:

$this->Picture->query("SELECT * FROM pictures AS Picture LIMIT 2;");

which returns

Array
(
    [0] => Array
        (
            [Picture] => Array
                (
                    [id] => 1304
                    [user_id] => 759
                )
        )

    [1] => Array
        (
            [Picture] => Array
                (
                    [id] => 1305
                    [user_id] => 759
                )
        )
)

This syntax and the corresponding array structure is valid for MySQL only. Cake does not provide any data abstraction when running queries manually, so exact results will vary between databases.

field¶

field(string $name, array $conditions = null, string $order = null)

Returns the value of a single field, specified as $name, from the first record matched by $conditions as ordered by $order. If no conditions are passed and the model id is set, will return the field value for the current model result. If no matching record is found returns false.

$this->Post->id = 22;
echo $this->Post->field('name'); // echo the name for row id 22

echo $this->Post->field('name', array('created <' => date('Y-m-d H:i:s')), 'created DESC'); // echo the name of the last created instance

read()¶

read($fields, $id)

read() is a method used to set the current model data (Model::$data)–such as during edits–but it can also be used in other circumstances to retrieve a single record from the database.

$fields is used to pass a single field name, as a string, or an array of field names; if left empty, all fields will be fetched.

$id specifies the ID of the record to be read. By default, the currently selected record, as specified by Model::$id, is used. Passing a different value to $id will cause that record to be selected.

read() always returns an array (even if only a single field name is requested). Use field to retrieve the value of a single field.

function beforeDelete($cascade) {
   ...
   $rating = $this->read('rating'); // gets the rating of the record being deleted.
   $name = $this->read('name', 2); // gets the name of a second record.
   $rating = $this->read('rating'); // gets the rating of the second record.
   $this->id = 3; //
   $this->read(); // reads a third record
   $record = $this->data // stores the third record in $record
   ...
}

Notice that the third call to read() fetches the rating of the same record read before. That is because read() changes Model::$id to any value passed as $id. Lines 6-8 demonstrate how read() changes the current model data. read() will also unset all validation errors on the model. If you would like to keep them, use find('first') instead.

The example above works if you run this code within the beforeDelete() method of the model itself. If you want to call read() from a controller, it would look something like this:

function article($action) {
   ...
   $this->Article->id = 3; //
   $this->Article->read(); // reads a third record
   $record = $this->Article->data // stores the third record in $record
   ...
}

Complex Find Conditions¶

Most of the model’s find calls involve passing sets of conditions in one way or another. The simplest approach to this is to use a WHERE clause snippet of SQL. If you find yourself needing more control, you can use arrays.

Using arrays is clearer and easier to read, and also makes it very easy to build queries. This syntax also breaks out the elements of your query (fields, values, operators, etc.) into discrete, manipulatable parts. This allows CakePHP to generate the most efficient query possible, ensure proper SQL syntax, and properly escape each individual part of the query.

At it’s most basic, an array-based query looks like this:

$conditions = array("Post.title" => "This is a post");
//Example usage with a model:
$this->Post->find('first', array('conditions' => $conditions));

The structure here is fairly self-explanatory: it will find any post where the title equals “This is a post”. Note that we could have used just “title” as the field name, but when building queries, it is good practice to always specify the model name, as it improves the clarity of the code, and helps prevent collisions in the future, should you choose to change your schema.

What about other types of matches? These are equally simple. Let’s say we wanted to find all the posts where the title is not “This is a post”:

array("Post.title <>" => "This is a post")

Notice the ‘<>’ that follows the field name. CakePHP can parse out any valid SQL comparison operator, including match expressions using LIKE, BETWEEN, or REGEX, as long as you leave a space between field name and the operator. The one exception here is IN (…)-style matches. Let’s say you wanted to find posts where the title was in a given set of values:

array(
    "Post.title" => array("First post", "Second post", "Third post")
)

To do a NOT IN(…) match to find posts where the title is not in the given set of values:

array(
    "NOT" => array("Post.title" => array("First post", "Second post", "Third post"))
)

Adding additional filters to the conditions is as simple as adding additional key/value pairs to the array:

array (
    "Post.title" => array("First post", "Second post", "Third post"),
    "Post.created >" => date('Y-m-d', strtotime("-2 weeks"))
)

You can also create finds that compare two fields in the database

array("Post.created = Post.modified")

This above example will return posts where the created date is equal to the modified date (ie it will return posts that have never been modified).

Remember that if you find yourself unable to form a WHERE clause in this method (ex. boolean operations), you can always specify it as a string like:

array(
    'Model.field & 8 = 1',
    //other conditions as usual
)

By default, CakePHP joins multiple conditions with boolean AND; which means, the snippet above would only match posts that have been created in the past two weeks, and have a title that matches one in the given set. However, we could just as easily find posts that match either condition:

array( "OR" => array (
    "Post.title" => array("First post", "Second post", "Third post"),
    "Post.created >" => date('Y-m-d', strtotime("-2 weeks"))
    )
)

Cake accepts all valid SQL boolean operations, including AND, OR, NOT, XOR, etc., and they can be upper or lower case, whichever you prefer. These conditions are also infinitely nest-able. Let’s say you had a belongsTo relationship between Posts and Authors. Let’s say you wanted to find all the posts that contained a certain keyword (“magic”) or were created in the past two weeks, but you want to restrict your search to posts written by Bob:

array (
    "Author.name" => "Bob",
    "OR" => array (
        "Post.title LIKE" => "%magic%",
        "Post.created >" => date('Y-m-d', strtotime("-2 weeks"))
    )
)

If you need to set multiple conditions on the same field, like when you want to do a LIKE search with multiple terms, you can do so by using conditions similar to:

 array(
    'OR' => array(
    array('Post.title LIKE' => '%one%'),
    array('Post.title LIKE' => '%two%')
    )
);

Cake can also check for null fields. In this example, the query will return records where the post title is not null:

array ("NOT" => array (
        "Post.title" => null
    )
)

To handle BETWEEN queries, you can use the following:

array('Post.id BETWEEN ? AND ?' => array(1,10))

Note: CakePHP will quote the numeric values depending on the field type in your DB.

How about GROUP BY?

array('fields'=>array('Product.type','MIN(Product.price) as price'), 'group' => 'Product.type');

The data returned for this would be in the following format:

Array
(
    [0] => Array
        (
            [Product] => Array
                (
                    [type] => Clothing
                )
            [0] => Array
                (
                    [price] => 32
                )
        )
    [1] => Array....

A quick example of doing a DISTINCT query. You can use other operators, such as MIN(), MAX(), etc., in a similar fashion

array('fields'=>array('DISTINCT (User.name) AS my_column_name'), 'order'=>array('User.id DESC'));

You can create very complex conditions, by nesting multiple condition arrays:

array(
   'OR' => array(
      array('Company.name' => 'Future Holdings'),
      array('Company.city' => 'CA')
   ),
   'AND' => array(
      array(
         'OR'=>array(
            array('Company.status' => 'active'),
            'NOT'=>array(
               array('Company.status'=> array('inactive', 'suspended'))
            )
         )
     )
   )
);

Which produces the following SQL:

SELECT `Company`.`id`, `Company`.`name`,
`Company`.`description`, `Company`.`location`,
`Company`.`created`, `Company`.`status`, `Company`.`size`

FROM
   `companies` AS `Company`
WHERE
   ((`Company`.`name` = 'Future Holdings')
   OR
   (`Company`.`name` = 'Steel Mega Works'))
AND
   ((`Company`.`status` = 'active')
   OR (NOT (`Company`.`status` IN ('inactive', 'suspended'))))

Sub-queries

For the example, imagine we have a “users” table with “id”, “name” and “status”. The status can be “A”, “B” or “C”. And we want to get all the users that have status different than “B” using sub-query.

In order to achieve that we are going to get the model data source and ask it to build the query as if we were calling a find method, but it will just return the SQL statement. After that we make an expression and add it to the conditions array.

$conditionsSubQuery['`User2`.`status`'] = 'B';

$dbo = $this->User->getDataSource();
$subQuery = $dbo->buildStatement(
    array(
        'fields' => array('`User2`.`id`'),
        'table' => $dbo->fullTableName($this->User),
        'alias' => 'User2',
        'limit' => null,
        'offset' => null,
        'joins' => array(),
        'conditions' => $conditionsSubQuery,
        'order' => null,
        'group' => null
    ),
    $this->User
);
$subQuery = ' `User`.`id` NOT IN (' . $subQuery . ') ';
$subQueryExpression = $dbo->expression($subQuery);

$conditions[] = $subQueryExpression;

$this->User->find('all', compact('conditions'));

This should generate the following SQL:

SELECT
    `User`.`id` ,
    `User`.`name` ,
    `User`.`status`
FROM
    `users` AS `User`
WHERE
    `User`.`id` NOT IN (
        SELECT
            `User2`.`id`
        FROM
            `users` AS `User2`
        WHERE
            `User2`.`status` = 'B'
    )

Also, if you need to pass just part of your query as raw SQL as the above, datasource expressions with raw SQL work for any part of the find query.

Saving Related Model Data (hasOne, hasMany, belongsTo)¶

When working with associated models, it is important to realize that saving model data should always be done by the corresponding CakePHP model. If you are saving a new Post and its associated Comments, then you would use both Post and Comment models during the save operation.

If neither of the associated model records exists in the system yet (for example, you want to save a new User and their related Profile records at the same time), you’ll need to first save the primary, or parent model.

To get an idea of how this works, let’s imagine that we have an action in our UsersController that handles the saving of a new User and a related Profile associated by belongsTo association. Your form would look something like this:

echo $form->create('User', array('action'=>'add'));
echo $form->input('first_name');
echo $form->input('last_name');

echo $form->input('Profile.address');
echo $form->input('Profile.telephone');

echo $form->end('Add');

Then using saveAll() you can save your data like this:

<?php
function add() {
    if (!empty($this->data)) {
        if ($this->User->saveAll($this->data)) {
            // User and Profile created successfully
        } else {
            // Error creating user
        }
    }
}
?>

As a rule, when working with hasOne, hasMany, and belongsTo associations, its all about keying. The basic idea is to get the key from one model and place it in the foreign key field on the other. Sometimes this might involve using the $id attribute of the model class after a save(), but other times it might just involve gathering the ID from a hidden input on a form that’s just been POSTed to a controller action.

To supplement the basic approach used above, CakePHP also offers a very handy method saveAll(), which allows you to validate and save multiple models in one shot. In addition, saveAll() provides transactional support to ensure data integrity in your database (i.e. if one model fails to save, the other models will not be saved either).

For transactions to work correctly in MySQL your tables must use InnoDB engine. Remember that MyISAM tables do not support transactions.

Let’s see how we can use saveAll() to save Company and Account models at the same time.

First, you need to build your form for both Company and Account models (we’ll assume that Company hasMany Account).

echo $form->create('Company', array('action'=>'add'));
echo $form->input('Company.name', array('label'=>'Company name'));
echo $form->input('Company.description');
echo $form->input('Company.location');

echo $form->input('Account.0.name', array('label'=>'Account name'));
echo $form->input('Account.0.username');
echo $form->input('Account.0.email');

echo $form->end('Add');

Take a look at the way we named the form fields for the Account model. If Company is our main model, saveAll() will expect the related model’s (Account) data to arrive in a specific format. And having Account.0.fieldName is exactly what we need.

The above field naming is required for a hasMany association. If the association between the models is hasOne, you have to use ModelName.fieldName notation for the associated model.

Now, in our companies_controller we can create an add() action:

function add() {
   if(!empty($this->data)) {
      //Use the following to avoid   validation errors:
      unset($this->Company->Account->validate['company_id']);
      $this->Company->saveAll($this->data, array('validate'=>'first'));
   }
}

That’s all there is to it. Now our Company and Account models will be validated and saved all at the same time. A quick thing to point out here is the use of array('validate'=>'first'); this option will ensure that both of our models are validated. Note that array('validate'=>'first') is the default option on cakephp 1.3.

my_model_count

class Image extends AppModel {
    var $belongsTo = array(
        'ImageAlbum' => array('counterCache' => true)
    );
}

class Image extends AppModel {
    var $belongsTo = array(
        'ImageAlbum' => array(
            'counterCache' => true,
            'counterScope' => array('Image.active' => 1) // only count if "Image" is active = 1
    ));
}

Saving Related Model Data (HABTM)¶

Saving models that are associated by hasOne, belongsTo, and hasMany is pretty simple: you just populate the foreign key field with the ID of the associated model. Once that’s done, you just call the save() method on the model, and everything gets linked up correctly.

With HABTM, you need to set the ID of the associated model in your data array. We’ll build a form that creates a new tag and associates it on the fly with some recipe.

The simplest form might look something like this (we’ll assume that $recipe_id is already set to something):

<?php echo $form->create('Tag');?>
    <?php echo $form->input(
        'Recipe.id',
        array('type'=>'hidden', 'value' => $recipe_id)); ?>
    <?php echo $form->input('Tag.name'); ?>
    <?php echo $form->end('Add Tag'); ?>

In this example, you can see the Recipe.id hidden field whose value is set to the ID of the recipe we want to link the tag to.

When the save() method is invoked within the controller, it’ll automatically save the HABTM data to the database.

function add() {

    //Save the association
    if ($this->Tag->save($this->data)) {
        //do something on success
    }
}

With the preceding code, our new Tag is created and associated with a Recipe, whose ID was set in $this->data[‘Recipe’][‘id’].

Other ways we might want to present our associated data can include a select drop down list. The data can be pulled from the model using the find('list') method and assigned to a view variable of the model name. An input with the same name will automatically pull in this data into a <select>.

// in the controller:
$this->set('tags', $this->Recipe->Tag->find('list'));

// in the view:
$form->input('tags');

A more likely scenario with a HABTM relationship would include a <select> set to allow multiple selections. For example, a Recipe can have multiple Tags assigned to it. In this case, the data is pulled out of the model the same way, but the form input is declared slightly different. The tag name is defined using the ModelName convention.

// in the controller:
$this->set('tags', $this->Recipe->Tag->find('list'));

// in the view:
$form->input('Tag');

Using the preceding code, a multiple select drop down is created, allowing for multiple choices to automatically be saved to the existing Recipe being added or saved to the database.

What to do when HABTM becomes complicated?

By default when saving a HasAndBelongsToMany relationship, Cake will delete all rows on the join table before saving new ones. For example if you have a Club that has 10 Children associated. You then update the Club with 2 children. The Club will only have 2 Children, not 12.

Also note that if you want to add more fields to the join (when it was created or meta information) this is possible with HABTM join tables, but it is important to understand that you have an easy option.

HasAndBelongsToMany between two models is in reality shorthand for three models associated through both a hasMany and a belongsTo association.

Consider this example:

Child hasAndBelongsToMany Club

Another way to look at this is adding a Membership model:

Child hasMany Membership
Membership belongsTo Child, Club
Club hasMany Membership.

These two examples are almost the exact same. They use the same amount and named fields in the database and the same amount of models. The important differences are that the “join” model is named differently and its behavior is more predictable.

When your join table contains extra fields besides two foreign keys, in most cases it’s easier to make a model for the join table and setup hasMany, belongsTo associations as shown in example above instead of using HABTM association.

delete¶

delete(int $id = null, boolean $cascade = true);

Deletes the record identified by $id. By default, also deletes records dependent on the record specified to be deleted.

For example, when deleting a User record that is tied to many Recipe records (User ‘hasMany’ or ‘hasAndBelongsToMany’ Recipes):

• if $cascade is set to true, the related Recipe records are also deleted if the models dependent-value is set to true.

• if $cascade is set to false, the Recipe records will remain after the User has been deleted.

deleteAll¶

deleteAll(mixed $conditions, $cascade = true, $callbacks = false)

Same as with delete() and remove(), except that deleteAll() deletes all records that match the supplied conditions. The $conditions array should be supplied as an SQL fragment or array.

conditions Conditions to match cascade Boolean, Set to true to delete records that depend on this record. Note that you will need to set dependent to true in the relevant model associations callbacks Boolean, Run callbacks

Relationship Types¶

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

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'
        )
    );
}

?>

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 for each model must be unique app wide. E.g. it is appropriate to have

<?php
class User extends AppModel {
    var $name = 'User';
    var $hasMany = array(
        'MyRecipe' => 'Recipe',
    );
    var $hasAndBelongsToMany = array('Member' => 'User');
}

class Group extends AppModel {
    var $name = 'Group';
    var $hasMany = array(
        'MyRecipe' => array(
            'className'  => 'Recipe',
        )
    );
    var $hasAndBelongsToMany = array('MemberOf' => 'Group');
}
?>

but the following will not work well in all circumstances:

<?php
class User extends AppModel {
    var $name = 'User';
    var $hasMany = array(
        'MyRecipe' => 'Recipe',
    );
    var $hasAndBelongsToMany = array('Member' => 'User');
}

class Group extends AppModel {
    var $name = 'Group';
    var $hasMany = array(
        'MyRecipe' => array(
            'className'  => 'Recipe',
        )
    );
    var $hasAndBelongsToMany = array('Member' => 'Group');
}
?>

because here we have the alias ‘Member’ referring to both the User (in Group) and the Group (in User) model in the HABTM associations. Choosing non-unique names for model aliases across models 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();

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();

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

hasOne¶

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:

Table: hasOne: the other model contains the foreign key.

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';
}
?>

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
        )
    );
}
?>

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
        )
)

belongsTo¶

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:

Table: belongsTo: the current model contains the foreign key.

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';
}
?>

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'
        )
    );
}
?>

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.”

• type: the type of the join to use in the SQL query, default is LEFT which may not fit your needs in all situations, INNER may be helpful when you want everything from your main and associated models or nothing at all!(effective when used with some conditions of course). (NB: type value is in lower case - i.e. left, inner)

• 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
        )
)

hasMany¶

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';
}
?>

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
        )
    );
}
?>

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 = {$__cakeID__$};
  

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.

hasAndBelongsToMany (HABTM)¶

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 Gnocchi 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.

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 Models

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'            => ''
            )
    );
}
?>

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');

//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')));

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
));

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')
));

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 Models

For more information on binding model associations on the fly see Models

Mix and match techniques to achieve your specific objective.

hasMany through (The Join Model)¶

It is sometimes desirable to store additional data with a many to many association. Consider the following

Student hasAndBelongsToMany Course Course hasAndBelongsToMany Student

In other words, a Student can take many Courses and a Course can be taken my many Students. This is a simple many to many association demanding a table such as this

id | student_id | course_id

Now what if we want to store the number of days that were attended by the student on the course and their final grade? The table we’d want would be

id | student_id | course_id | days_attended | grade

The trouble is, hasAndBelongsToMany will not support this type of scenario because when hasAndBelongsToMany associations are saved, the association is deleted first. You would lose the extra data in the columns as it is not replaced in the new insert.

The way to implement our requirement is to use a join model, otherwise known (in Rails) as a hasMany through association. That is, the association is a model itself. So, we can create a new model CourseMembership. Take a look at the following models.

student.php

class Student extends AppModel
{
    public $hasMany = array(
        'CourseMembership'
    );

    public $validate = array(
        'first_name' => array(
            'rule' => 'notEmpty',
            'message' => 'A first name is required'
        ),
        'last_name' => array(
            'rule' => 'notEmpty',
            'message' => 'A last name is required'
        )
    );
}

course.php

class Course extends AppModel
{
    public $hasMany = array(
        'CourseMembership'
    );

    public $validate = array(
        'name' => array(
            'rule' => 'notEmpty',
            'message' => 'A course name is required'
        )
    );
}

course_membership.php

class CourseMembership extends AppModel
{
    public $belongsTo = array(
        'Student', 'Course'
    );

    public $validate = array(
        'days_attended' => array(
            'rule' => 'numeric',
            'message' => 'Enter the number of days the student attended'
        ),
        'grade' => array(
            'rule' => 'notEmpty',
            'message' => 'Select the grade the student received'
        )
    );
}

The CourseMembership join model uniquely identifies a given Student’s participation on a Course in addition to extra meta-information.

Working with join model data¶

Now that the models have been defined, let’s see how we can save all of this. Let’s say the Head of Cake School has asked us the developer to write an application that allows him to log a student’s attendance on a course with days attended and grade. Take a look at the following code.

controllers/course_membership_controller.php

class CourseMembershipsController extends AppController
{
    public $uses = array('CourseMembership');

    public function index() {
        $this->set('course_memberships_list', $this->CourseMembership->find('all'));
    }

    public function add() {

        if (! empty($this->data)) {

            if ($this->CourseMembership->saveAll(
                $this->data, array('validate' => 'first'))) {


                $this->redirect(array('action' => 'index'));
            }
        }
    }
}

views/course_memberships/add.ctp

<?php echo $form->create('CourseMembership'); ?>
    <?php echo $form->input('Student.first_name'); ?>
    <?php echo $form->input('Student.last_name'); ?>
    <?php echo $form->input('Course.name'); ?>
    <?php echo $form->input('CourseMembership.days_attended'); ?>
    <?php echo $form->input('CourseMembership.grade'); ?>
    <button type="submit">Save</button>
<?php echo $form->end(); ?>

You can see that the form uses the form helper’s dot notation to build up the data array for the controller’s save which looks a bit like this when submitted.

Array
(
    [Student] => Array
        (
            [first_name] => Joe
            [last_name] => Bloggs
        )

    [Course] => Array
        (
            [name] => Cake
        )

    [CourseMembership] => Array
        (
            [days_attended] => 5
            [grade] => A
        )

)

Cake will happily be able to save the lot together and assigning the foreign keys of the Student and Course into CourseMembership with a saveAll call with this data structure. If we run the index action of our CourseMembershipsController the data structure received now from a find(‘all’) is:

Array
(
    [0] => Array
        (
            [CourseMembership] => Array
                (
                    [id] => 1
                    [student_id] => 1
                    [course_id] => 1
                    [days_attended] => 5
                    [grade] => A
                )

            [Student] => Array
                (
                    [id] => 1
                    [first_name] => Joe
                    [last_name] => Bloggs
                )

            [Course] => Array
                (
                    [id] => 1
                    [name] => Cake
                )

        )

)

There are of course many ways to work with a join model. The version above assumes you want to save everything at-once. There will be cases where you want to create the Student and Course independently and at a later point associate the two together with a CourseMembership. So you might have a form that allows selection of existing students and courses from picklists or ID entry and then the two meta-fields for the CourseMembership, e.g.

views/course_memberships/add.ctp

<?php echo $form->create('CourseMembership'); ?>
    <?php echo $form->input('Student.id', array('type' => 'text', 'label' => 'Student ID', 'default' => 1)); ?>
    <?php echo $form->input('Course.id', array('type' => 'text', 'label' => 'Course ID', 'default' => 1)); ?>
    <?php echo $form->input('CourseMembership.days_attended'); ?>
    <?php echo $form->input('CourseMembership.grade'); ?>
    <button type="submit">Save</button>
<?php echo $form->end(); ?>

And the resultant POST

Array
(
    [Student] => Array
        (
            [id] => 1
        )

    [Course] => Array
        (
            [id] => 1
        )

    [CourseMembership] => Array
        (
            [days_attended] => 10
            [grade] => 5
        )

)

Again Cake is good to us and pulls the Student id and Course id into the CourseMembership with the saveAll.

Join models are pretty useful things to be able to use and Cake makes it easy to do so with its built-in hasMany and belongsTo associations and saveAll feature.

Creating and Destroying Associations on the Fly¶

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';
}

?>

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');
}

Removing or adding associations using bind- and unbindModel() only works for the next find 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'))
);

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');
}

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...
                )
            )
        )
    );

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.

Multiple relations to the same model¶

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'
        )
    );
}
?>

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'
        )
    );
}
?>

It is also possible to create self associations as shown below.

<?php
class Post extends AppModel {
    var $name = 'Post';

    var $belongsTo = array(
        'Parent' => array(
            'className' => 'Post',
            'foreignKey' => 'parent_id'
        )
    );

    var $hasMany = array(
        'Children' => array(
            'className' => 'Post',
            'foreignKey' => 'parent_id'
        )
    );
}
?>

An alternate method of associating a model with itself (without assuming a parent/child relationship) is to have both the $belongsTo and $hasMany relationships of a model each to declare an identical alias, className, and foreignKey [property].

<?php
class MySchema extends CakeSchema {
    public $users = array (
        'id' => array ('type' => 'integer', 'default' => null, 'key' => 'primary'),
        'username' => array ('type' => 'string', 'null' => false, 'key' => 'index'),
        // more schema properties...
        'last_user_id' => array ('type' => 'integer', 'default' => null, 'key' => 'index'),

        'indexes' => array (
            'PRIMARY' => array ('column' => 'id', 'unique' => true),
            // more keys...
            'last_user' => array ('column' => 'last_user_id', 'unique' => false)
        )
    );
}

class User extends AppModel {
    public $hasMany = array (
        'Tag' => array (
            'foreignKey' => 'last_user_id'
        ),
        // more hasMany relationships...
        'LastUser' => array (
            'className' => 'User',
            'foreignKey' => 'last_user_id'
        )
    );
    public $belongsTo = array (
        // in most cases this would be the only belongsTo relationship for this model
        'LastUser' => array (
            'className' => 'User',
            'foreignKey' => 'last_user_id',
            'dependent' => true
        )
    );
}
?>