Update some content

[eluser]sam_weiss[/eluser]
Hi people, i'm new in codeigniter and i'm very excited.
But now I got stuck on a problem. I am not able to edit the content via a form.

Controller:

Code:

class Site extends CI_Controller{
    
function index(){
    $data['records'] = $this->data_model->get();
    $this->load->view('home', $data);
    
    
}

function delete(){
    
  $this->data_model->delete();
  redirect('site/index');
    
}
function add(){
    $tables['title'] = $this->input->post('title');
    $tables['content'] = $this->input->post('content');
    $tables['id'] = $this->input->get('entry_id');
   $this->data_model->add($tables);
   redirect('site/index');
}

function update(){
    
    $tables['title'] =  $this->input->post('title');
    $tables['content'] = $this->input->post('content');
   $this->data_model->update($tables);
  redirect('site/index');
  
}


function comments(){
    
     $this->load->view('commentsview');

}

Function update in Model:

Code:

function update($tables){
    
    
      $this->db->set('id', $this->uri->segment(3));
      $this->db->update('data', $tables);
  }

Commentsview(View):

Code:

<?php echo form_open('site/update'); ?>
<label for="title">Title:</label>
&lt;input type="text" name="title" /&gt;
<label for="content">Content:</label>
&lt;input type="textarea" rows="10" name="content"&gt; &lt;/textarea&gt;
<p>&lt;input type="submit" value="Enviar" /&gt; </p>
&lt;?php echo form_close(); ?&gt;

So it gives me this error:

A Database Error Occurred
Error Number: 1062

Duplicate entry '0' for key 1

UPDATE `data` SET `id` = 0, `title` = 'title', `content` = 'content'

Filename: C:\xampp\htdocs\ci\system\database\DB_driver.php

Line Number: 330

Someone help me? And sorry my english.