$marks=0;
$correct = 0;
while ($row=mysqli_fetch_assoc($result)){
    $exam_name = $row['exam_name'];
    $exam_percentage = $row['exam_pass_percentage'];
    if($row['a_sortorder'] == $json['responses'][0][1][$row['qid']]){
        $marks = $marks + 4;
        $correct++;
    }
}