Severity: Notice Message: Undefined variable: img when trying to upload to server - codeigniter

Question

I'm trying to update my information: In the localhost it is not error variable: img, but when i upload it into the server it is error like that A PHP Error was encountered:
Severity: Notice Message: Undefined variable: img Filename: controllers/pages.php Line Number: 79....
function update_ads($id)
{
if($this->input->post('update_ads'))
{
$this->db->select('img');
$this->db->where('id',$id);
$query = $this->db->get('tblp_label_slides',$id);
foreach($query->result() as $row)
{
$img = $row->img;
$image = $this->session->set_userdata('img', $img);
}
if($img!='')
{
$config['upload_path'] ='./images/ads';
$config['allowed_types'] ='jpg|jpeg|gif|png';
$config['max_size'] = 1024*8;
$config['encrypt_name'] = true;
$this->upload->initialize($config);
$this->load->library('upload', $config);
if(!$this->upload->do_upload('imgfile'))
{
$edit['update'] = $this->mod_write->up_adv($this->session->userdata('img'), $id);
$this->session->set_flashdata(array('success_update' => 12));
redirect('pages/ads_right');
}
else
{
$img_content = $this->upload->data('imgfile');
$edit['update'] = $this->mod_write->up_adv($img_content['file_name'], $id);
unlink("./images/ads/".$img);
$this->session->set_flashdata(array('success_update' => 12));
redirect('pages/ads_right');
}
}
else
{
$config['upload_path'] = './images/ads';
$config['allowed_types'] = 'jpg|jpeg|gif|png';
$config['max_size'] = 1024*8;
$config['encrypt_name'] = true;
$this->upload->initialize($config);
$this->load->library('upload', $config);
if(! $this->upload->do_upload('imgfile'))
{
$edit['update'] = $this->mod_write->up_adv('', $id);
$this->session->set_flashdata(array('success_update' => 12));
redirect('pages/ads_right');
}
else
{
$img_content = $this->upload->data('imgfile');
$edit['update'] = $this->mod_write->up_adv($img_content['file_name'], $id);
unlink("./images/ads/".$img);
$this->session->set_flashdata(array('success_update' => 12));
redirect('pages/ads_right');
}
}
}
}
my model
function up_adv($img_content)
{
$id = $this->uri->segment(3);
$data = array(
'dates'=>date('Y-m-d H:i:s'),
'url'=>replace_tag($this->input->post('url')),
'title'=>replace_tag($this->input->post('title')),
'img'=>$img_content,
'type'=>$this->input->post('type')
);
$this->db->where('id',pde($id))
->update('tblp_label_slides',$data);
}

Answer 1

I could be wrong but I think the issue how you are validating $img.
Change if ($img != '')
To if (isset($img) && trim($img) !== '')
This will stop an error being thrown if $img has not been declared which will happen if your query doesn't return any rows.
Hope this helps!