Why is my 20 digit random number always the same?

Code:

public function send($per_id = NULL) {



  $securitycode = $this->Enter_detail->gen_string();

  $this->load->model('Email');

  $this->load->model('Notifications');

  $data['type'] = 'Most popular';

  if ((!is_numeric($per_id)) or ($per_id < 0)) {$per_id = 0;} //get page number variable from URI and set if not unsigned integer

  if ($this->input->post('gift'))

   {

   $mathcode = strip_tags($this->input->post('code'));

   //first check if math captcha is correct

   if ($mathcode != $this->session->userdata('realcd'))

    {

    $error = $this->notificationmssgs->errors();

    $this->session->set_flashdata('error', $error[22]);

    redirect('home/page');

    }

   //check if member has sent per_id a message in last 24 hours

   if ($this->Enter_detail->check_if_gift_before($this->session->userdata('mem_id'), $per_id))

    {

    $error = $this->notificationmssgs->errors();

    $this->session->set_flashdata('error', $error[20]);

    redirect(base_url('home/page/search'));

    }   

   $filtermssg = $this->Messagefilter->filter($this->input->post('message'));

   $this->Enter_detail->submit_gift($this->input->post('gift'), $per_id, $filtermssg, $securitycode);

   $this->Email->add_notification($per_id, $this->session->userdata('mem_id'), 'has sent you a gift!');

   $this->Notifications->add_notification($per_id, $this->session->userdata('mem_id'), 'gift', $securitycode);

   $notification = $this->notificationmssgs->notifications();

   $this->session->set_flashdata('message', $notification[11]);

   redirect('home/page/search');

   }

  $data['type'] = $this->input->post('type');

  //check that member is permitted to message per_id

  if ($this->Extract_detail->check_if_banned($per_id)) {

   $error = $this->notificationmssgs->errors();

   $this->session->set_flashdata('error', $error[14]);

   redirect(base_url('home/page/search'));

   }

  //get username of per_id

  $data['username'] = $this->Extract_detail->get_username($per_id);

  $data['per_id'] = $per_id;

  

  //choose which gifts to load based on member selection

  $data['gifts'] = $this->Extract_detail->gift_selection($data['type']);

  

  $this->load->view('blocks/spacer');

  $this->load->view('blocks/notificationbar', $data);

  $this->load->view('gift-send', $data);

  $data['bottomscript'] = '[removed][removed]';

  $this->load->view('blocks/footer', $data);  



}//SEND

Code:

public function gen_string() {



  $this->load->helper('string');

  return random_string('numeric', 20);



 }//gen_string



public function submit_gift($id, $per_id, $message, $seccode) {



  $this->load->helper('date');

  $datetime = unix_to_human(time(), TRUE, 'eu');

  $data = array(

   'id' => $seccode,

   'gift_id' => $id,

   'mem_id' => $this->session->userdata('mem_id'),

   'per_id' => $per_id,

   'message' => $message,

   'datetime' => $datetime

   );

  $this->db->insert('network_gifts', $data);



 }//submit_gift