i have this code for submitting an online exam and i submit this page using javascript xmlhttprequest(pure javascript no Jquery) and i have three parameters the question id arrays and answers and the numbers of rows 

<?php
require_once ("../templates/header.php");
 ?>
<?php
    require_once ("../core/initialize.php");
 ?>
<?php $total_of_questions = null; ?>
<div class="container">
    <div>
        <span class="total-of-questions" style="margin-right: 10px;font-size: 19px;">   <?php echo $total_of_questions; ?></span>
        <span class="exam-time" style="float: left;margin-left: 10px;font-size: 19px;">     :  30 </span>
    </div>
 <div class="submit-exam-div" id="submit-exam-div">
<?php
if (isset($_POST["exam-submit-button"])) {

    $questions_id_array = $_POST["questions_id_array"];
    $total_questions = $_POST["rowCount"];
    $exam -> correct_exam($questions_id_array, $total_questions);

} // End of submit
?>    
 </div> <!------End Of Submit Div-------->
 
 <div class="spinner" id="spinner" style="display: none;">
     <img src="../multimedia/ajax_spinner/ajax-spinner.gif" />
 </div>
 
 <div class="question-div" id="question-div" style="display: block;">   
<form action="<?php echo $_SERVER["PHP_SELF"];   ?>" method="post" id="exam-form" name="exam-form">
<?php
//$question_type_id = 2 ;
//$question_type_id = isset($_GET["question_type_id"]) ?  $_GET["question_type_id"] :  false ; 
$question = $exam->find_question_for_exam(2);
$rowCount = $question->rowCount();
$total_of_questions = $question->columnCount();
$question_rows = $question->fetchAll(PDO::FETCH_CLASS,"Exam");
$question_number = 1 ;
  foreach ($question_rows as $question_row ):?>
<hr style="border: 1px  dotted #E38D33; width: auto; "/>
<ol>
		<p style="font-size: 19px;margin-right:10px; margin-bottom: 10px;">    <?php echo $question_number; ?> # </p>
        <p style="font-size: 22px;"><?php echo $question_row -> question_text; ?></p>
        <?php $question_number++; ?>
<?php
 // Get answers from Database
 $answer = $exam->find_answer_for_question($question_row->question_id);
 $answer_rows = $answer->fetchAll(PDO::FETCH_CLASS,"Exam");
 foreach ($answer_rows as $answer_row):?>
        <li style="font-size: 20px;"><input type="radio" name="answer<?php echo $question_row -> question_id; ?>" value="<?php echo $answer_row -> answer_text; ?>" />
        <?php echo $answer_row -> answer_text . "<br />"; ?></li>
   <?php endforeach ; // End foreach for answers fetch ?>   
<li><input type="hidden" name="questions_id_array[]" value="<?php echo $question_row -> question_id; ?>" ></li>
</ol>
   <?php endforeach ; // End foreach for questions fetch ?>
<hr style="border: 1px  dotted #E38D33; width: auto; "/>
    <input type="hidden" name="rowCount" value="<?php echo $rowCount; ?>" >
    <!---<input type="submit" name="question_submit" id="question-submit" value=" " />---->
    <button name="exam-submit-button" id="exam-submit-button" > </button>
</form>      
</div> <!------End of question DIV----------->
</div> <!------End of container DIV----------->
<?php //require_once ("../templates/footer.php"); ?>
<script type="text/javascript">

	var spinner = document.getElementById("spinner");

	function showSpinner() {

		spinner.style.display = "block";
	}

	function hideSpinner() {

		spinner.style.display = "none";
	}

	function submitExam() {

		var xmlhttp;

		var submit_exam_div = document.getElementById("submit-exam-div");

		var answer = document.getElementById("answer").value;
		var questions_id = document.getElementById("questions_id_array").value;
		var row_count = document.getElementById("rowCount").value;

		var input_parameters = "answer=" + answer + "&questions_id=" + questions_id + "&row_count=" + row_count;

		xmlhttp = new XMLHttpRequest();
		xmlhttp.open("POST", "exam.php", true);
		xmlhttp.setRequestHeader("Content-Type,application/x-www-form-urlencoded; charset=UTF-8");
		xmlhttp.onreadystatechange = function() {

			if (xmlhttp.readyState == 2) {

				showSpinner();

			}

			if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {

				hideSpinner();

				submit_exam_div.innerHTML = xmlhttp.responseText;

			}
		};

		xmlhttp.send(input_parameters);

	}

	var question_submit = document.getElementById("exam-submit-button");
	question_submit.addEventListener("click", submitExam);

	function hideQuestionDiv() {
		var question_div = document.getElementById("question-div");

		if (question_div.style.display = "block") {
			question_div.style.display = "none";
			return true;
		} else {
			question_div.style.display = "block";
			return false;
		}
	}

	var button = document.getElementById("exam-submit-button")
	button.addEventListener("click", hideQuestionDiv);
</script>
<pre>
	<?php print_r($_POST); ?>
</pre>