BelongsToMany associated record won't save in join table - cakephp

Question

I have 2 tables "Descriptions" and "Phases", associated BelongsToMany using a join Table "DescriptionsPhases", as per Cakephp naming conventions. I've been struggling with this for the best part of a day now: I just cannot get the controller to save the id's of description and phase into my join table, which is basically just 3 columns, id / description_id / phase_id. Possibly more may follow for metadata.
Here is my code structure:
In Descriptions Table:
$this->belongsToMany('Phases', [
'foreignKey' => 'description_id',
'targetForeignKey' => 'phase_id',
'through' => 'DescriptionsPhases',
'saveStrategy' => 'append'
]);
In Phases Table:
$this->belongsToMany('Descriptions', [
'foreignKey' => 'phase_id',
'targetForeignKey' => 'description_id',
'through' => 'DescriptionsPhases'
]);
In DescriptionsPhases Table:
$this->belongsTo('Descriptions', [
'foreignKey' => 'description_id',
'joinType' => 'INNER'
]);
$this->belongsTo('Phases', [
'foreignKey' => 'phases_id',
'joinType' => 'INNER'
]);
In Entities of all 3 of the above (for now):
protected $_accessible = [
'*' => true
];
In Descriptions Controller, add() method. The id for $descriptions->phases is hardcoded for now, just to reduce complexity:
public function add() {
$description = $this->Descriptions->newEntity([
'associated' => ['Phases']]);
if ($this->request->is('post')) {
// additional data to be saved in new description
$description->user_id = $this->Auth->user('id');
$description->designvariant = 666;
// Hardcoded integer TO BE SAVED in associated model (via join table)
$description->phases = [['id' => 5]];
$patch = $this->Descriptions->patchEntity($description, $this->request->getData(), [
'associated' => ['Phases']]);
debug($patch);
$save = $this->Descriptions->save($patch);
debug($save);
if ($save) {
$this->Flash->success(__('The description has been saved.'));
return $this->redirect(['action' => 'index']);
}
$this->Flash->error(__('The description could not be saved. Please, try again.'));
}
// pass arrays for dropdown menus
$this->set('trades', ($this->Descriptions->Trades->listLabels()));
$this->set('elements', ($this->Descriptions->Elements->listLabels()));
$this->set('allocations', ($this->Descriptions->Allocations->listLabels()));
$this->set(compact('description'));
$this->render();
}
I have debugged both after patchEntity and saveEntity, and get this data structure.
debug($patch);
object(App\Model\Entity\Description) {
'associated' => [
(int) 0 => 'Phases'
],
'user_id' => (int) 1,
'designvariant' => (int) 666,
'phases' => [
(int) 0 => [
'id' => (int) 5
]
],
'element_id' => 'A',
'shorttext' => 'title',
'longtext' => 'text',
'trade_id' => '0',
'allocation_id' => 'BMST',
'[new]' => true,
'[accessible]' => [
'trade_id' => true,
'element_id' => true,
'allocation_id' => true,
'shorttext' => true,
'longtext' => true,
'designvariant_id' => true,
'user_id' => true,
'created' => true,
'modified' => true,
'trade' => true,
'element' => true,
'allocation' => true,
'phase' => true,
'phases' => true,
'designvariant' => true,
'user' => true,
'amounts' => true,
'costs' => true,
'descriptions_phases' => true,
'descriptions_phase' => true,
'*' => true
],
'[dirty]' => [
'associated' => true,
'user_id' => true,
'designvariant' => true,
'phases' => true,
'element_id' => true,
'shorttext' => true,
'longtext' => true,
'trade_id' => true,
'allocation_id' => true
],
'[original]' => [],
'[virtual]' => [],
'[errors]' => [],
'[invalid]' => [],
'[repository]' => 'Descriptions'
}
debug($save);
object(App\Model\Entity\Description) {
'associated' => [
(int) 0 => 'Phases'
],
'user_id' => (int) 1,
'designvariant' => (int) 666,
'phases' => [
(int) 0 => [
'id' => (int) 5
]
],
'element_id' => 'A',
'shorttext' => 'title',
'longtext' => 'text',
'trade_id' => '0',
'allocation_id' => 'BMST',
'created' => object(Cake\I18n\FrozenTime) {
'time' => '2019-01-11T10:04:32+00:00',
'timezone' => 'UTC',
'fixedNowTime' => false
},
'modified' => object(Cake\I18n\FrozenTime) {
'time' => '2019-01-11T10:04:32+00:00',
'timezone' => 'UTC',
'fixedNowTime' => false
},
'id' => (int) 133,
'[new]' => false,
'[accessible]' => [
'trade_id' => true,
'element_id' => true,
'allocation_id' => true,
'shorttext' => true,
'longtext' => true,
'designvariant_id' => true,
'user_id' => true,
'created' => true,
'modified' => true,
'trade' => true,
'element' => true,
'allocation' => true,
'phase' => true,
'phases' => true,
'designvariant' => true,
'user' => true,
'amounts' => true,
'costs' => true,
'descriptions_phases' => true,
'descriptions_phase' => true,
'*' => true
],
'[dirty]' => [],
'[original]' => [],
'[virtual]' => [],
'[errors]' => [],
'[invalid]' => [],
'[repository]' => 'Descriptions'
}
The record is saved smoothly into the Descriptions Table, but it just won't save any associated data.
Am I missing something obvious?
Any help is gratefully received. Also, if you need more info, plz ask as it's my 1st post here :-)

Answer 1

Only entities are being saved, ie phases must hold an array of entities, not nested arrays. The nested arrays are what you'd pass to newEntity()/patchEntity(), where they would be converted into entities accordingly.
$description->phases = [
$this->Descriptions->Phases->get(5)
];
See also
Cookbook > Database Access & ORM > Saving Data > Saving With Associations
Cookbook > Database Access & ORM > Saving Data > Saving Entities > Saving Associations