Association fields

Use CakePHP's property paths to choose related records or edit nested data. Load the associations you want to edit before binding the entity.

Choose related records

For an article with Authors and Tags associations, supply option lists from your controller. These snippets belong to your existing edit action and view.

ArticlesController::edit() — view data

$article = $this->Articles->get($id, contain: ['Tags']);
$authors = $this->Articles->Authors->find('list');
$tags = $this->Articles->Tags->find('list');

$this->set(compact('article', 'authors', 'tags'));

templates/Articles/edit.php

<?php
$form = $this->Form->bind($article);
?>
<?= $form->open() ?>
<?= $form->control('author_id')
    ->choices($authors)
    ->placeholder('No author') ?>
<?= $form->control('tags._ids')->choices($tags) ?>
<?= $form->submit('Save article') ?>
<?= $form->close() ?>

author_id is a single select. tags._ids is a multiple select, with the article's loaded tags selected. Choosing author 7 and tags 2 and 5 submits:

[
    'author_id' => '7',
    'tags' => ['_ids' => ['2', '5']],
];

Pass this data to your normal CakePHP patchEntity() and save workflow with the appropriate association configuration.

Choice discovery and explicit overrides

With conventional field and view-variable names, you can omit choices():

// Uses the $authors and $tags view variables set above.
echo $form->control('author_id');
echo $form->control('tags._ids');

An _id field looks for its pluralized view variable. A ._ids selector looks for the collection's variable. FormCompose reads those lists; it does not query the database for them. Explicit choices() takes priority, including an empty list. Use it for nonconventional names or to make the source visible at the call.

For a checkbox presentation:

echo $form->control('tags._ids')
    ->type('multicheckbox')
    ->choices($tags);

Edit associated records

Load Details and Comments in the controller's existing article query, then render their property paths inside the open article form:

echo $form->control('details.id');
echo $form->control('details.summary');
echo $form->control('comments.0.id');
echo $form->control('comments.0.body');

comments.0.body submits comments[0][body]. Associated schemas supply types, validation constraints, and errors. Known primary keys render as hidden inputs. Use repeated blueprints when every comment needs the same set of fields.

Edit values on a join record

For editable belongsToMany junction data, use CakePHP's _joinData property. With loaded tags whose primary key is id, render:

echo $form->control('tags.0.id');
echo $form->control('tags.0._joinData.priority');

Use this form of nested record editing when editing each link's data. Use tags._ids when choosing a set of related records.

Validation feedback and empty selections

An error on tags appears on its tags._ids control. Nested errors appear next to their corresponding fields. Clearing the tags selection submits an empty value, allowing your application to remove the old selection.

Your application still controls association accessibility, validation, and saving. See association conventions for custom property names, primary keys, inferred types, and empty-value behavior.

Reuse associated field configuration

A parent blueprint can embed a child at author, or repeat a child at comments. Follow blueprint composition and repeated embeds for complete declarations and views.