Retrieve data from many to many relationship in Laravel - php

Question

I know the question has been responded many times, but for some reason I couldn't make it work for my tables, no matter what, and I don't understand why.
I've been trying this for like 4 hours and I couldn't get it done right.
So here are my functions from two models:
ConducatorDoctorat
public function materii()
{
return $this->belongsToMany('App\DomeniuDoctorat', 'profesor_domeniu', 'domeniu_id', 'profesor_id');
}
DomeniuDoctorat
public function materii()
{
return $this->belongsToMany('App\ConducatorDoctorat', 'profesor_domeniu', 'profesor_id', 'domeniu_id');
}
and profesor_domeniu schema:
<?php
use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;
class ProfesorDomeniu extends Migration
{
/**
* Run the migrations.
*
* #return void
*/
public function up()
{
Schema::create('profesor_domeniu', function (Blueprint $table) {
$table->unsignedBigInteger('profesor_id');
$table->unsignedBigInteger('domeniu_id');
$table->foreign('profesor_id')
->references('id')->on('conducatori_doctorat')
->onDelete('cascade');
$table->foreign('domeniu_id')
->references('id')->on('domenii_doctorat')
->onDelete('cascade');
});
}
/**
* Reverse the migrations.
*
* #return void
*/
public function down()
{
Schema::dropIfExists('profesor_domeniu');
}
}
In my controller, I tried so many ways to do it, for example, like this:
public function edit($id)
{
$materii = ConducatorDoctorat::findOrFail($id)->materii()->pluck('domeniu_id');
return view('admin.conducatori_doctorat.edit')->with([
'materii' => $materii
]);
}
but it still doesn't work.
With the given $id, I want to retrieve all the data from profesor_domeniu where profesor_id == $id.
That's all, but I can't get it.
How can this be done and why doesn't my approach work?
//edit for clarity:
conducator_doctorat is where the professors are stored and domenii_doctorat is where their fields are stored.
In profesor_domeniu, I store what each professor teaches, by linking an id from conducatori_doctorat to an id of a field from domenii_doctorat.
//edit2:
materii() means the fields they teach.
//edit3:
My many-to-many relationship with some data added into the pivot table profesor_domeniu.

Answer 1

eager load your relationship on your model :
public function edit($id)
{
$conducatorDoctorat = ConducatorDoctorat::with('materii')->findOrFail($id);
$materii = $conducatorDoctorat->materii;
return view('admin.conducatori_doctorat.edit')->with([
'materii' => $materii
]);
}
you can also request only your materii related to your conducatorDoctorat :
public function edit($id)
{
$materii = DomeniuDoctorat::whereHas('materii', function($query) use ($id){
$query->where('id', $id);
})->get();
return view('admin.conducatori_doctorat.edit')->with([
'materii' => $materii
]);
}