PHP - sorting arrays in group

I have trouble sorting my array result in a different way. I have written an API call that returns specified results but not in the right way.

So it gives me:

{
"success": true,
"data": [
    [
        "Question",
        [
            "Answer"
        ]
    ],
    [
        "Question",
        [
            "Answer 2"
        ]
    ],
    [
        "Question 2",
        [
            "Answer 3"
        ]
    ]
],
"message": null

}

And I want to return a group of answers for that question like:

{
"success": true,
"data": [
    [
        "Question",
        [
            "Answer"
        ],
        [
            "Answer 2"
        ]
    ],
    [
        "Question 2",
        [
            "Answer 3"
        ]
    ]
],
"message": null
}

And my code looks like:

$questions = $this->getQRepository()->findAll();

$mappedQuestions = [];

foreach ($questions as $question){

    $title = $question->getTitle();

    $mappedQuestions[] = [
        $title,
        [
            $question->getAnswer()
        ]
    ];
}

return $mappedQuestions;

It gives me the result where it groups every question with answer by id but I need to group all answers by question. The result returns correctly but sorting is wrong.

This might work, but I'm not sure if this is what you are looking for. So first, modified your current looping and $mappedQuestions array structure like this:

$mappedQuestions = [];

foreach ($questions as $question){

    $mappedQuestions[] = array(
                               'title' => $question->getTitle(), 
                               'answer' => $question->getAnswer()
                          );
}

After that, iterate the array one more time to create a new array that will group together the elements based on the array key, which in this case is "title".

$sorted = array();
foreach ($mappedQuestions as $element) {
    $sorted[$element['title']][] = $element['answer'];
}

return $sorted;

The final output of $sorted is:

{
   "Question":[
      "Answer",
      "Answer 2"
   ],
   "Question 2":[
      "Answer 3"
   ]

The sort looping code is actually from this question.

I hope this help.