PHP-MySQL+CodeIgniter无法显示patient_category表数据求助

我用CodeIgniter的视图、模型、控制器代码展示数据库中patient_category表的数据，但页面未显示任何内容，也没有错误提示，不清楚问题出在哪个环节，希望得到排查帮助。

视图页面代码 #

<section id="main-content">
    <section class="wrapper site-min-height">
        <!-- page start-->
        <section class="panel">
          <header class="panel-heading">
          <?php echo lang('patient_categorie'); ?>
           <div class="col-md-4 no-print pull-right"> 
            <a data-toggle="modal" href="#myModal">
            <div class="btn-group pull-right">
             <button id="" class="btn green btn-xs">
          <i class="fa fa-plus-circle"></i> <?php echo lang('crer_p_categorie'); ?>
             </button>
             </div>
            </a>
           </div>
          </header>
            <div class="panel-body">
            <div class="adv-table editable-table ">
             <div class="space15"></div>
             <table class="table table-striped table-hover table-bordered" id="editable-sample">
               <thead>
                <tr>
                 <th> <?php echo lang('patient_categorie'); ?></th>
                 <th> <?php echo lang('patient_categorie_description'); ?></th>
                 <th> <?php echo lang('options'); ?></th>
                </tr>
               </thead>
               <tbody>

               <style>
                .img_url{
                   height:20px;
                   width:20px;
                   background-size: contain; 
                   max-height:20px;
                   border-radius: 100px;
                 }
                </style>
            <?php 
               foreach ($categories as $category) { ?>
               <tr class="">
                <td><?php echo $category->category; ?></td>
                <td> <?php echo $category->description; ?></td>
                <td>
        <button type="button" class="btn btn-info btn-xs btn_width editbutton" data-toggle="modal" data-id="<?php echo $category->id; ?>"><i class="fa fa-edit"> <?php echo lang('edit'); ?></i>
     </button>   
<a class="btn btn-info btn-xs btn_width delete_button" href="patient/deletePatientCategorie?id=<?php echo $category->id; ?>" onclick="return confirm('Etes-vous sûr de vouloir supprimer cet élément?');"><i class="fa fa-trash-o"> <?php echo lang('delete'); ?></i></a>
                </td>
               </tr>
            <?php } ?>

             </tbody>
         </table>
       </div>
     </div>
 </section>

模型获取数据函数 #

function getPatientCategory() {
        $this->db->where('hospital_id', $this->session->userdata('hospital_id'));
        $query = $this->db->get('patient_category');
        return $query->result();
    }

控制器代码 #

public function patientCategory() {
        if (!$this->ion_auth->logged_in()) {
            redirect('auth/login', 'refresh');
        }
        $data['categories'] = $this->patient_model->getPatientCategory();
        $data['settings'] = $this->settings_model->getSettings();
        $this->load->view('home/dashboard', $data); // just the header file
        $this->load->view('femme_enceinte', $data);
        $this->load->view('home/footer'); // just the header file
    }

    public function addCategoryView() {
        $data['settings'] = $this->settings_model->getSettings();
        $this->load->view('home/dashboard', $data); // just the header file
        $this->load->view('add_new_category');
        $this->load->view('home/footer'); // just the header file
    }

    public function addNewCategory() {
        $id = $this->input->post('id');
        $category = $this->input->post('category');
        $description = $this->input->post('description');

        $this->load->library('form_validation');
        $this->form_validation->set_error_delimiters('<div class="error">', '</div>');
        // Validating Category Name Field
        $this->form_validation->set_rules('category', 'Category', 'trim|required|min_length[2]|max_length[100]|xss_clean');
        // Validating Description Field
        $this->form_validation->set_rules('description', 'Description', 'trim|required|min_length[5]|max_length[100]|xss_clean');
        if ($this->form_validation->run() == FALSE) {
            $data['settings'] = $this->settings_model->getSettings();
            $this->load->view('home/dashboard', $data); // just the header file
            $this->load->view('add_new_category');
            $this->load->view('home/footer'); // just the header file
        } else {
            $data = array();
            $data = array('category' => $category,
                'description' => $description
            );
            if (empty($id)) {
                $this->patient_model->insertPatientCategory($data);
                $this->session->set_flashdata('feedback', 'Ajouté');
            } else {
                $this->patient_model->updatePatientCategory($id, $data);
                $this->session->set_flashdata('feedback', 'Modifié');
            }
            redirect('patient/patientCategory');
        }
    }

    function edit_category() {
        $data = array();
        $id = $this->input->get('id');
        $data['patient'] = $this->patient_model->getPatientCategoryById($id);
        $data['settings'] = $this->settings_model->getSettings();
        $this->load->view('home/dashboard', $data); // just the header file
        $this->load->view('add_new_category', $data);
        $this->load->view('home/footer'); // just the footer file
    }

    function editPatientCategoryByJason() {
        $id = $this->input->get('id');
        $data['patientcategory'] = $this->patient_model->getPatientCategoryById($id);
        echo json_encode($data);
    }

    function deletePatientCategory() {
        $id = $this->input->get('id');
        $this->patient_model->deletePatientCategory($id);
        $this->session->set_flashdata('feedback', 'Supprimé');
        redirect('patient/patientCategory');
    }

• 开启错误提示：在项目根目录的index.php里，把ENVIRONMENT常量改成'development'，同时确保display_errors开启，这样能显示隐藏的PHP或数据库错误。
• 验证数据是否获取成功：在控制器的patientCategory方法里，$data['categories'] = ...之后加一行var_dump($data['categories']); die;，查看是否有数据返回。如果为空：
  • 检查数据库patient_category表中是否存在对应hospital_id的记录
  • 用var_dump($this->session->userdata('hospital_id'));验证会话中是否存在有效的hospital_id
  • 核对模型方法里的表名、字段名是否拼写正确
• 确认视图加载正确性：检查控制器中加载的femme_enceinte视图是否就是你提供的展示分类的视图，有没有加载错误的文件。
• 检查视图变量是否存在：在视图的foreach循环前加var_dump($categories);，确认变量是否成功传递到视图，有没有拼写错误（比如控制器里是categories，视图里写成了其他名字）。
• 调试数据库查询：在模型的getPatientCategory方法里，return之前加echo $this->db->last_query(); die;，把生成的SQL语句复制到数据库管理工具中执行，看是否能得到结果。
• 检查登录状态：确认用户已正常登录，ion_auth->logged_in()是否返回true，会不会因为未登录直接跳转但没有提示。

内容的提问来源于stack exchange，提问作者Denis yele