如何检查更新复选框？

I had an issue when edit checkbox. Checkbox not cheked when edit. I'm using codeigniter.

This is my model:

public function categories_post($id)
    {
        $this->db->select('categories.idcategory, categories.category_name');
        $this->db->from('categories');
        $this->db->join('categories_detail', 'categories_detail.idcategory = categories.idcategory', 'inner');
        $this->db->join('posts', 'posts.idpost = categories_detail.idpost', 'inner');
        $this->db->where('posts.idpost', $id);
        return $this->db->get();
    }

This my controller:

public function edit($id='')
    {
        $data['post'] = $this->posts->getpostbyid('posts',$id);
        $data['a'] = $this->posts->categories_post($id)->row_array();
        $data['tags'] = $this->posts->tags_post($id);

        $data['media'] = $this->datamedia->list_image();
        $data['title']="Edit Pos";
        $data['file']="posts/editpost";
        $data['categories'] = $this->posts->getallcategories('categories');
        $this->load->view('form_template',$data);
    }

View :

<?php


foreach ($categories as $data) { ?>
          <div class="form-group">
            <input <?php if($a['idcategory']){ echo 'checked'; } ?> type="checkbox" name="category[]" value="<?php echo $data->idcategory ?>">&nbsp;&nbsp;<?php echo $data->category_name ?>
          </div>
       <?php } ?>

How can i make it checked ?

enter image description here enter image description here

i just updated my qustion. it always showing just 1 checked box althought i have more categories. (sorry my english not good)

Try to change the checkbox input to :

<input <?php echo $data->idcategory == $a['idcategory'] ? 'checked' : '' ?> type="checkbox" name="category[]" value="<?php echo $data->idcategory ?>">&nbsp;&nbsp;<?php echo $data->category_name ?>

Solved. I just add foreach inside input tag in my view

<?php
   foreach ($categories as $data) { ?>
     <div class="form-group">
       <input <?php foreach ($a as $aa) { echo $data->idcategory == $aa['idcategory'] ? 'checked' : ''; } ?> type="checkbox" name="category[]" value="<?php echo $data->idcategory ?>">&nbsp;&nbsp;<?php echo $data->category_name ?>
     </div>
<?php } ?>