I got a favor to ask:

$test = $request->test_id;

$questions = LearnQuestion::leftJoin('learn_answers', 'learn_questions.id', '=', 'learn_answers.question_id')->where('test_id', '=', $test)->get();

It shows information in array form:

"id" => "1"
"name" => "Question 1"
"type_question" => "Single Choice"
"point" => "10"
"test_id" => "1"
"created_at" => "2022-09-02 10:13:01"
"updated_at" => "2022-09-02 10:13:01"
"answer" => "Answer 1"
"question_id" => "1"
"correct" => "No"
"id" => "2"
"name" => "Question 1"
"type_question" => "Single Choice"
"point" => "10"
"test_id" => "1"
"created_at" => "2022-09-02 10:13:01"
"updated_at" => "2022-09-02 10:13:01"
"answer" => "Answer 2"
"question_id" => "1"
"correct" => "Yes"

How do I put them into one nested arrays, like this:

Array
(

• => Array

(

• => 'Question 1'
[1]=> 'Answer 1'
[2]=> 'Answer 2'
[3]=> 'Answer 3'
)
[1] => Array
(

• => 'Question 2'
[1]=> 'Answer 1'
[2]=> 'Answer 2'
[3]=> 'Answer 3'
)
)

I tried to this

$data = null;
while ($row = $questions) {
$data[$row['question_id']][0] = $row['name'];
$data[$row['question_id']][$row['id']] = $row['answer'];
}

But it gives and error "Undefined index: question_id

The error you're encountering suggests that the way you're attempting to access the indexes of your result set might be causing problems.

First off, you're trying to loop through `$questions`, which is an instance of a collection and not a single row. You should iterate through it properly. Here's a revised approach to accomplish what you're aiming for:

$data = [];
foreach ($questions as $row) {
    // Initialize the question if not already done
    if (!isset($data[$row->question_id])) {
        $data[$row->question_id] = [];
        $data[$row->question_id][0] = $row->name; // Store the question name
    }
   
    // Add the answer to the question
    $data[$row->question_id][] = $row->answer; // Store the answer
}

In this change, I'm using a `foreach` loop to go through each row in `$questions`. For each row, it checks if the question already exists in the `$data` array using `question_id` as a key. If not, it initializes that question entry and adds the question name. Then, it appends the answer to the same question entry.

This should yield a nested array structured similar to what you're looking for:

Array
(
    [1] => Array
        (
            [0] => 'Question 1'
            [1] => 'Answer 1'
            [2] => 'Answer 2'
        )
    [2] => Array
        (
            [0] => 'Question 2'
            [1] => 'Answer 1'
            [2] => 'Answer 2'
        )
)
Make sure that `question_id` in your database rows is properly indexed and accessible. If you continue to experience issues, check that the dataset actually has the values and that there are no spelling mistakes in your variable names.

This should help you create that nested structure without running into undefined index errors. Just remember that debugging is often about closely examining your data and ensuring that you're working with it correctly.

Why go through the trouble of executing a leftJoin manually when building a relationship could be simpler? If you were to create an 'answers' relationship for the LearnQuestion model, you'd only need a simple line like this:

$questions = LearnQuestion::with('answers')->where('test_id', $test)->get();

Then, to display this data in your view, you can use the following:

@foreach ($questions as $question)
<div>{{ $question->name }}</div>
@foreach ($question->answers as $answer)
<label>
<input type="radio" name="answers[{{ $question->id }}]" value="{{ $answer->id }}">
{{ $answer->answer }}
</label>
@endforeach
@endforeach

It's a lot cleaner and way more effiecent. Utilizing the relationships makes your code more understandable, resulting in better maintainability down the line.

Eloquent takes care in naming fields according to the class name itself. For instance, it creates the field name learn_question_id, but your database table uses question_id instead. Additionally, this is a one-to-many relationship, which is different from a many-to-many setup.

To fix this issue, you got to manually define the field name in your code:

public function answers()
{
return $this->hasMany(LearnAnswer::class, 'question_id');
}

public function question()
{
return $this->belongsTo(LearnQuestion::class, 'question_id');
}
Make sure to always align your field names with your database to prevent confusion and ensure smooth functionality.