如何在codeigniter php中编辑时从多选下拉列表和显示中获取数据

Question

从多选下拉列表中获取数据并使用codeigniter php更新数据。无法从多选下拉列表中获取数据。在添加数据时，它正在成功插入。但是当我尝试获取要编辑的数据时，无法获取多选下拉列表。

控制器：

export GYP_DEFINES="OS=android"
gn gen out/Default --args='target_os="android" target_cpu="arm"'

型号：

function edit()
{
  $data['categorylist']=$this->blogs_model->categories_dropdown();
  $data['records']= $this->blogs_model->getblogsdata($this->uri->segment(3));
  $data['mainpage']='blogs';
  $data['mode']='edit';
  $this->load->view('templates/template',$data);
}

function editblogs()
{
    $this->load->library('form_validation');
    $this->form_validation->set_error_delimiters('<br /><span class="message error"> ','</span>');
    $this->form_validation->set_rules('category_id','Category Name','required');        
    $this->form_validation->set_rules('blog_title','Blog Title');
    if($this->form_validation->run()== FALSE)   
    {         
        $data['categorylist']=$this->blogs_model->categories_dropdown();
        $data['records']=$this->blogs_model->getblogsdata($this->input->post('blog_id'));
        $data['mainpage']='blogs';
        $data['mode']='edit';
        $this->load->view('templates/template',$data);  
    }   
        else    
        {       
            $result = $this->blogs_model->update($this->input->post('blog_id'));        
            if(is_array($result))
            {       
                $data['errors']=$result;
                $data['records']=$this->blogs_model->getblogsdata($this->uri->segment('blog_id'));             
                $data['mainpage']='blogs';
                $data['mode']='edit';
                $this->load->view('templates/template',$data);  
            }                              
                else                    
                $this->flash->success('<h2>Successfully Updated the record.<h2>');                      
                redirect('blogs');                  
        }                       
}

查看：

function getblogsdata($id)
{
    $this->db->select('blogs.*,C.category_name');       
    $this->db->from('blogs');
    $this->db->join('categories AS C','C.category_id=blogs.category_id','INNER');
    $this->db->where(array('blogs.blog_id'=>$id));      
    $q=$this->db->get();        
    if($q->num_rows()>0)
      {
    return $q->result();
        }
    else
    {
    return false;
    }
}

function update($id)
{
    $data=array(
    'blog_title'=>$this->input->post('blog_title')      
    );
    $this->db->where(array('blog_id'=>$id));
    $this->db->update('blogs', $data);
    return true;

    $options = $this->input->post('category_id');   
    foreach($options as $opt){
    $data1=array(
    'category_id'=>$opt
    );
    $this->db->where(array('blog_id'=>$id));
    $this->db->update('blog_categories',$data1);
    }       
}