title: I can't delete record in Codeigniter
body: <p>I'm learning CRUD in codeigniter. I have table name "posting" and the coloumns are like this (id, title, post).
  I successed to create a new post (both insert into database and display in the view). But I have problem when I delete my post in the front-end. Here is my code:</p>
  
  <p>Model</p>
  
  <pre><code>Class Post_Model extends CI_Model{
    function index(){
       //Here is my homepage code
    }
  
    function delete_post($id)
    {
       $this-&gt;db-&gt;where('id', $id);
       $this-&gt;db-&gt;delete('posting');
    }
  }
  </code></pre>
  
  <p>Controller</p>
  
  <pre><code>Class Post extends CI_Controller{
    function delete()
    {
       $this-&gt;load-&gt;model('Post_Model');
       $this-&gt;Post_Model-&gt;delete_post("id");
  
       redirect('Post/index/', 'refresh');
    }
  }
  </code></pre>
  
  <p>After click "delete" in the homepage, there was nothing happens. While I'm looking into my database, my records still available.</p>
  
  <p>Note: 
  (1) to delete record, I'm following the codeigniter manual / user guide, 
  (2) I found a message error (Undefined variable: id) after hiting the "delete" button in the front-end</p>
  
  <p>Any help or suggestion, please</p>