value not insert into database using php codeigniter - php

Question

I am trying to insert the data to the database by php CodeIgniter and display the result in the same page during submit the button. Below is my code.The problem is i got an error message as Duplicate entry '104' for key 'PRIMARY'. Please help. View Page
<div class="container col-lg-4">
<?php echo validation_errors(); ?>
<form action="<?php echo base_url();?>index.php/Welcome/gallery1" method="post">
<div class="form-group has-info">
<?php
foreach ($h->result_array() as $value){
?>
<input type="hidden" name="id" value="<?php echo $value['offer_id'];?>" >
<?php }?>
<br>
<label class="control-label col-lg-6" for="inputSuccess">Offer title</label>
<input type="text" class="form-control col-lg-6" name="offered" id="offered" value="<?php if(isset($_POST['offered'])) echo $_POST['offered']; ?>">
<label class="control-label col-lg-6" for="inputSuccess">Offer Description</label>
<textarea id="description" name="description" class="form-control col-lg-6" rows="3" value="<?php if(isset($_POST['description'])) echo $_POST['description']; ?>" ></textarea>
<br/>
<div>
<button type="submit" class="btn btn-primary col-lg-4"> <span>SUBMIT</span>
</button>
</div>
</div>
</form>
Controller page
public function gallery1()
{
$this->load->helper('url');
$this->load->helper('form');
$this->load->library('form_validation');
$this->load->model('Login_set');
$this->form_validation->set_rules('id','id');
$this->form_validation->set_rules('offered','offered','required');
$this->form_validation->set_rules('description','description','required');
$page_id =$this->uri->segment(3);
$data['h']=$this->Login_set->select();
$this->load->view('App_stay/pages/hotel1_galery.php',$data);
if($this->form_validation->run() == FALSE)
{
}
else
{
$data['query']=$this->Login_set->add_offer();
if($data['query']!=NULL)
{
$data['ins_msg']='data inserted';
}
else
{
$data['ins_msg']='data not inserted';
}
}
}
Model Page
public function add_offer()
{
$this->form_validation->set_message('offered','offered','required');
$this->form_validation->set_message('description','description','required');
$this->load->database();
$this->load->helper('url');
$data=array
(
'offer_id'=>$this->input->post('id'),
'hotel_id'=>1,
'offers_name'=>$this->input->post('offered'),
'offers_description'=>$this->input->post('description')
);
$this->db->insert('offer_hotel1',$data);
}