如何格式化必须写在csv文件Codeigniter上的数据

I need help writing my data in a csv file in a particular format. I have json data as follows

[ { "name": "Abc", "class": "12", "date": "14-04-2018", "answers": "question1 : answer1, q2 : a2, q3 : a3, q4 : a4" } ]

I am storing the decoded version of this json in $details array. I have to write this data in a csv file. Here is my current code-

 $filename = 'logs_'.$id.'.csv'; 
 header("Content-Description: File Transfer"); 
 header("Content-Disposition: attachment; filename=$filename"); 
 header("Content-Type: application/csv; ");
 $file = fopen('php://output', 'w');
 $header = array("name","class","date","answers"); 
 fputcsv($file, $header);
 foreach ($details as $key=>$line){ 
    fputcsv($file,$line); 
 }
 fclose($file);
 exit;

I need this data in a particular format. I have attached the image containing both the current output and the required output. I want the answers to be written in separate rows as shown in the image.

(I have asked a similar question before but I had to delete it since it was ill-formed so please do not flag it) I want to achieve this without using any external libraries or pluggins. SO if you have any idea on how to achieve this then please let me know. Also, i was advised by one of the users on stackoverflow to use control break but i couldn't figure out a solution. If anyone else thinks thats the solution then please guide me

the only way i can imagine is to restructure the array

something like that should work

$str = '[
    {
        "name": "Abc",
        "class": "12",
        "date": "14-04-2018",
        "answers": "question1 : answer1, q2 : a2, q3 : a3, q4 : a4"
    },
    {
        "name": "Abc",
        "class": "12",
        "date": "14-04-2018",
        "answers": "question1 : answer1, q2 : a2, q3 : a3, q4 : a4"
    }
]';

$arrData = [];
$arrJsonData = json_decode($str);

foreach($arrJsonData AS $objItem)
{
    $arrAnswers = explode(',', $objItem->answers);
    $objItem->answers = (count($arrAnswers) > 0)    ?   array_shift($arrAnswers)    :   array();

    $arrData[] = $objItem;

    if (count($arrAnswers) > 0)
    {
        foreach($arrAnswers AS $val)
        {
            $objNew = new stdClass();
            $objNew->name = '';
            $objNew->class = '';
            $objNew->date = '';
            $objNew->answers = $val;

            $arrData[] = $objNew;

        }
    }
}

print_r($arrData);