ajax기초에 대해 질문드립니다...

<select name="theme_select" id="theme_select" class="theme_select">
<? while($row = mysqli_fetch_array($result)){?>
<option value="<?=$row['No']?>"><?=$row['class_theme']?></option>
<?}?>
 </select>
           <input type="text"  id="tete" class="tete">
 <script>
                  var theme_selection = $("#theme_select option:checked").text();
                        alert(theme_selection);
                        $("#theme_select").change(function () {
                        alert($(this).children("option:selected").text());
                                $('#tete').html('');
                                 $.ajax({
                                  url: 'ajax.code.php',
                                  dataType: 'json',
                                  type: 'POST',
                                 data: {'theme_select': $('#theme_select').val()},
                                 success: function(result){
                                    if(result['tete']==true){                                                                                                           $('#tete').html(result['theme_select']);        
                                        }
                                  }
                         });
                   });                           
                                                                </script>

 

<!-----------------------ajax.code.php--->

<?php
echo json_encode(array('tete'=>true, 'theme_select'=>$_REQUEST['theme_select']));
?>