Post CURL Request of JSON Data with while loop

I'm sending a post request to an end point using while loop to send several values to the "questions" sub-array as seen below but it says "bad request". The body of the data has a sub-array into which I need to send multiple entries fetching from the database. Do I need a foreach loop instead?

  $sql= "SELECT * FROM table WHERE quiz_id = $quiz_id";
                   while ($row_que =mysqli_fetch_array($sql)) {
                   $question = $row_que['question'];
                   $marks = $row_que['marks'];
                   $optionA = $row_que['optionA'];
                   $optionB = $row_que['optionB'];
                   $optionC = $row_que['optionC'];
                   $optionD = $row_que['optionD'];
                   $optionE = $row_que['optionE'];
                   $correct_option = $row_que['correct_option'];

                      $data =
                      array(
                            'id' => '2',
                            'quizName' => 'Third Semester',
                            'numberOfQuestions' => '10', 
                            'isTimed' => true,                         
                            'numberOfMinutesToComplete' => '10',
                            'targetedClass' => '10',
                            'subject' => 'English',
                            'schoolLevel' => 'Grade 1',
                            'questions' =>  array(['question' => $question, 'questionMark' => $marks, 
                                                            'options' => array(['option' => 'A', 'answer'=> $optionA ], ['option' => 'B', 'answer' => $optionB] , ['option' => 'C', 'answer' => $optionC ], ['option' => 'D',
                                                            'answer' => $optionD ], ['option' => 'E', 'answer' => $optionE]),
                                                            'hasImage' => true,
                                                            'images' => array(['images-1' => 'image-1'], ['images-2' => 'image-2']),
                                                            'correctionOption' => $correct_option
                                       ]),
                           'totalValidMarks' => '10',
                            'validUntil' => '20-08-2020'
                            );

                    }

                        // API URL
                        $url = 'https://my-end-point';
                        // Create a new cURL resource

            $params = $data;
            $data_string = json_encode($data);
            $curl = curl_init();
            $curl = curl_init();
            curl_setopt_array($curl, array(
                CURLOPT_URL => $url,
                CURLOPT_RETURNTRANSFER => true,
                CURLOPT_ENCODING => "",
                CURLOPT_MAXREDIRS => 10,
                CURLOPT_TIMEOUT => 30,
                CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
                CURLOPT_CUSTOMREQUEST => "POST",
                CURLOPT_POSTFIELDS => $data_string,
                CURLOPT_HTTPHEADER => array(
                    "x-access-token: $token",
                    "cache-control: no-cache",
                    "content-type: application/json",
                ),
            ));

            $response = curl_exec($curl);
            $err = curl_error($curl);
            curl_close($curl);
            if ($err) {
                echo "cURL Error #:" . $err;
            } else {
                echo $response;
            }



                // echo $payload;
                }  

        }