In a php session

Question

}

put returns between paragraphs for linebreak add 2 spaces at end italic or bold indent code by 4 spaces backtick escapes like _so_ quote by placing > at start of line to make links (use https whenever possible)

Answer 1

You could have another session that stores the answers as an array, and add to it after each successful post

Something like this could work:

 <?php
    $totalQuestions = count($ques);
    $_SESSION['answers'] = $_SESSION['answers'] ?? [];
    // Get current question, default to 1
    $currentQuestion = count($_SESSION['answers']) == $totalQuestions ? 
        $totalQuestions : 
        $_SESSION['answers'] + 1;
?>

<div class='questionHeader'>
    <label>Question <?php echo $currentQuestion ?> of <?php echo $totalQuestions ?></label>
</div>

<br>

<div class='question'>
    <?php echo $ques[$currentQuestion-1] ?>
</div>

Answer: <input type='text' id='answerOneSub' name='answerOneSub'>
<button type='submit' value='submit' name='submit'>Submit!</button>
 
<?php
    if (isset($_POST['submit'])) {
        $_SESSION['answers'][] = $_POST['answerOneSub'];
        echo "<br>" . $_SESSION['answerOneSub'];
    }
?>