Fatal error: Call to undefined function redirect()

[eluser]Rocky Mehta[/eluser]
<code>
if ($this->input->post('upload'))
{
if ($this->input->post('capacity_view_id'))
{
$this->venue_capacity_model->do_upload();
$data['capacity_image'] = $this->venue_capacity_model->get_images();
$this->venue_capacity_model->update_capacity($_FILES['userfile']['name']);
echo "Data Updated Successfully";
redirect('http://localhost/venue/index.php/venue_capacity/update/');
}
else
{
$this->venue_capacity_model->do_upload();
$data['images'] = $this->venue_capacity_model->get_images();
$this->venue_capacity_model->insert_capacity($_FILES['userfile']['name']);
echo "Data Inserted Successfully";
}
}
</code>

Data Updated Successfully
Fatal error: Call to undefined function redirect() in D:\www\vhosts\localhost\venue\application\controllers\venue_capacity.php on line 25
Its give me error like this.

I am try to simple redirect my page but not working. please gave me solution how can i redirect my page.