unlink() function not worked

[eluser]harris_priambudi[/eluser]
I want to delete data from database and delete image file at once in one models..
when its execute
delete data from database succes, but the image file still exist from the folder where I used to stored image file data..
there is the models code:

Code:

$location_logo="http://localhost/jobtagger_ci/file_data/logo/logo.png";
$lowongan=$this->input->post('id');

$tables = array('lowongan_data', 'lamaran_data');
$this->db->where('lowongan_id', $lowongan);
$this->db->delete($tables);
       unlink($location_logo);

im sorry for my bad english.. thanks for attention and ur help