CakePHP belongsToMany jointable -

i'm making blog , want able assign multiple categories or tags article , article can have multiple categories.

this have in database: articles, categories , join table articles_categories.

project:

join table:

in table/articlestable.php:

 public function initialize(array $config)  {      $this->addbehavior('timestamp');      $this->belongstomany('categories', [          'alias' => 'categories',          'foreignkey' => 'article_id',          'targetforeignkey' => 'category_id',          'jointable' => 'articles_categories'      ]);  } 

in table/categoriestable.php:

 public function initialize(array $config)  {      $this->table('categories');      $this->displayfield('name');      $this->primarykey('id');      $this->addbehavior('timestamp');       $this->belongstomany('articles', [          'alias' => 'articles',          'foreignkey' => 'category_id',          'targetforeignkey' => 'article_id',          'jointable' => 'articles_categories'      ]);  } 

when user adds article, needs add article , ids in join table here's articlescontroller/add method:

 public function add()  {      $article = $this->articles->newentity();       if ($this->request->is('post'))      {          $article = $this->articles->patchentity($article, $this->request->data);          $article->user_id = $this->auth->user('id');           if ($result = $this->articles->save($article))          {              $this->flash->success(__('your article has been saved.'));              return $this->redirect(['action' => 'index']);          }          $this->flash->error(__('unable add article.'));      }      $this->set(['article'=>$article,'buttontext'=>'add article']);      $categories = $this->articles->categories->find('list');     $this->set(compact('categories'));  } 

add.ctp view:

echo $this->form->create($article, ['class' => 'form-group']); echo $this->form->input('articlecategory',['options' => $categories,'id'=>'magicselect','multiple'=>true,'class'=>'form-control']); echo $this->form->input('title', ['class'=>'form-control',     'maxlength'=>'50']); echo $this->form->input('body', ['rows' => '8',     'class'=>'form-control',     'style'=>'margin-bottom:10px;resize: none',     'maxlength'=>'5000']); echo $this->form->button(__($buttontext), ['class'=>'btn btn-success']); echo $this->form->end(); 

and after submitting form debug($this->request->data):

[     'articles_categories' => [         (int) 0 => '1'     ],     'title' => 'test article',     'body' => 'lorem ipsum dolor sit amet, consectetuer adipiscing elit. aenean commodo ligula eget dolor. aenean massa.' ] 

my problem i'm not sure if associations correct. how automatically insert data in join table?

the property name

that not correct format belongstomany association, see

• http://book.cakephp.org/3.0/en/orm/associations.html#belongstomany-associations
• http://book.cakephp.org/3.0/en/views/helpers/form.html#associated-form-inputs

the property name should default underscored, plural name of association, in case categories.

the magic _ids key

since want link article existing categories, should additionally use magic _ids key pass ids of selected categories, marshaller take care of rest, pick , insert appropriate category entities based on given ids, see

http://book.cakephp.org/3.0/en/orm/saving-data.html#converting-belongstomany-data

all need append field/propertyname, categories._ids, ie form input should defined this:

$this->form->input('categories._ids', [     'options' => $categories,     'id' => 'magicselect',     'multiple' => true,     'class' => 'form-control' ]); 

note it's not necessary explicitly pass options, if follow conventions, ie use underscored plural of association name, form helper able automagically pick variable other input fields.