无法将数据更新到数据库（codeigniter）

i have this code in my update function, when i try other value the table updates but when i used that value($field8) the table don't update.

   public function edit_lead() {
       $id = "3";
       $field8 ="http://38.102.225.87/RECORDINGS/MP3/20170201-094849_7188352209-all.mp3";
       $this->db->set('field8', $field8);
       $this->db->where('id', $id);
       $query = $this->db->update('table');
       if($query) {
            return true;
       } else {
            return false;
       }
   }

Simply send the id of the user as a parameter of this function..

public function edit_lead($ID) { }