Save data into 2 tables cakephp 3 - forms

Question

I am very new to Cakephp 3. I try to do saveAll function in Cakephp 3, but unsuccessful.
I have 2 tables : Merchants and Users
Relationship between this 2 tables as below:
Users hasMany Merchants,
Merchants belongsTo Users
I want the create a merchant's registration form that will insert the data to both tables.
Can someone help me how to insert data into 2 different tables from 1 form using Cakephp 3?
My code as below:
<?= $this->Form->create($merchant); ?>
<fieldset>
<legend><?= __('Add Merchant') ?></legend>
<?php
echo $this->Form->input('User.id');
echo $this->Form->input('User.username');
echo $this->Form->input('User.password');
echo $this->Form->input('merchant_type_id', ['options' => $merchantTypes]);
echo $this->Form->input('name');
echo $this->Form->input('identity_number');
echo $this->Form->input('phone_number');
?>
</fieldset>
<?= $this->Form->button(__('Submit')) ?>
<?= $this->Form->end() ?>
Controller:
public function registration()
{
$merchant = $this->Merchants->newEntity();
if ($this->request->is('post')) {
$merchant = $this->Merchants->patchEntity($merchant, $this->request->data, [
'associated' => ['Users']
]);
if ($this->Merchants->saveAll($merchant)) {
$this->Flash->success('The merchant has been saved.');
return $this->redirect(['action' => 'index']);
} else {
$this->Flash->error('The merchant could not be saved. Please, try again.');
}
}
$users = $this->Merchants->Users->find('list', ['limit' => 200]);
$merchantTypes = $this->Merchants->MerchantTypes->find('list', ['limit' => 200]);
$this->set(compact('merchant', 'users', 'merchantTypes'));
}
Your helps is very appreciated. Thanks.

Answer 1

I think your problem is that your fields aren't named by lower-underscored version of the association name.
Instead of put:
echo $this->Form->input('User.username')
Which would result:
<input type="text" name="User[username]" >
You should try to put something as:
echo $this->Form->input('user.username');
Which would result:
<input type="text" name="user[username]" >
I hope it would be useful :)
PS: Sorry if there's any grammar mistakes but English is not my native language ;)

Answer 2

Please follow the documentation for saving data:
http://book.cakephp.org/3.0/en/orm/saving-data.html
If you are coming from 2.x, read the ORM migration guide, it should answer most of your questions:
http://book.cakephp.org/3.0/en/appendices/orm-migration.html