how to load code on php just one time

this is a part of code php page, and i just want to load the code for one time so, when i load the page (full of code page (include the code bellow)) if the code bellow have loaded one time then the code bellow can't loaded.

I have code like this :

    $notif = $userData['pemberitahuan'];

        $userId = $userData['id'];
        $ket = 'unread';

        $update_data = array(
            'pemberitahuan' => $ket
        );


        $this->db->where('id', $userId);
        $query = $this->db->update('user', $update_data);

        return ($query === true) ? true : false;


?>

So how i can load this code for one time? and doesn't loaded when the page of full code is load or refresh??