<input class="answer" type="text" name="answer" size="16"  value="<?php echo (isset(($_POST["answer"] ))  ? htmlspecialchars($_POST["answer"]) : '' ?>" autocomplete="off">

<?php echo (isset(($_POST["answer"] ))  ? htmlspecialchars($_POST["answer"]) : '' ?>

$.ajax({
    url: '../php/action.php',
    type: 'POST',
         success: function(data) {
          $('.answer').test(data);
         });