Ionic Framework，从数据库中填充select（drowdownlist）

Question

以下代码出了什么问题？我可以直接通过任何浏览器获取JSON结果，它只是不想显示在下拉列表中

我只是想在离子框架中从mysql数据库填充到组合框。

更新的脚本

在下拉列表中仍然为空。任何人吗？

addlist.html

<ion-header-bar align-title="center" class="bar-stable">
  <h1 class="title">Add Lists</h1>
</ion-header-bar>
<ion-view>
  <div class="list has-header padding">
    <label class="item item-input item-select">
      <div class="input-label">
        Category
      </div>
      <div ng-controller="AddListCategoryCtrl">
        <select ng-model="category" ng-options="x.category for x in data">
          <option ng-repeat="x in data" value="{{x.id}}">{{x.category}}</option>
        </select>
      </div>
    </label>
  </div>
</ion-view>

controllers.js

angular.module('ionicApp.controllers', [])

.controller('AddListCategoryCtrl', function($scope, $http) {
    var xhr = $http({
      method: 'post',
      url: 'http://www.mywebsite.com/api/listCat.php'
    });
    xhr.success(function(data){
      $scope.data = data.data;
    });
});

listCat.php

<?php
include 'db.php';
getById();

function getById() {
    $sql = "SELECT id,category FROM tbl_category ORDER BY tbl_category.id";
    try {
        $db = getDB();
        $stmt = $db->prepare($sql);
        $stmt->execute();
        $category = $stmt->fetchAll(PDO::FETCH_OBJ);
        $db = null;
        echo '{"category": ' . json_encode($category) . '}';

    } catch(PDOException $e) {
        echo '{"error":{"text":'. $e->getMessage() .'}}';
    }
}
?>