NEED HELP - Error Undefined Variable

hi senior,
 
i still learning CI, i have problem
 
this is my code :
 
$id_p = $this->db->query('select max(id) as max_id from products')->row();        
        $store = $this->Setting_model->get_outlet_all();      
        foreach ($store as $st) {
            
            $countIfStoreExist = $this->Products_model->countIfStoreExist($st->id,$id); --> this is cause error
thanks all