数学方法没有扣除/更新PHP Codeigniter

Question

我尝试在下面应用代码，在php中没有显示任何错误，但结果却没有更改/更新。请帮我解决这个问题。谢谢你的帮助。

  

$ saldo = $ by-＆gt; saldo - $ server-＆gt; Price;

在控制器中：

public function renew_account($id=FALSE) {
    $this->load->library('sshcepat');
    if (empty($this->user_model->id_ssh($id)->hostname)) { Show_404(); }
    $create_by = $this->user_model->id_ssh($id)->created_by;
    $server = $this->user_model->get_hostname($id);
    $by = $this->user_model->get_user($_SESSION['user_id']);

   $data = array (
        'hostname' => $this->user_model->id_ssh($id)->hostname,
        'rootpass' => $this->user_model->get_hostname($this->user_model->id_ssh($id)->serverid)->RootPasswd,
        'username' => $this->user_model->id_ssh($id)->username,
        'expired' => $this->user_model->id_ssh($id)->expired_at
    );
    if ( isset($_SESSION['username']) && $_SESSION['logged_in'] === true ) {
            if($_SESSION['username'] === $create_by ) {
             if ($this->user_model->renew_user_ssh($id)) {

                $saldo = $by->saldo - $server->Price;
                if ($this->user_model->update_saldo($by->username, $saldo)) {

                    if ($this->sshcepat->renewAccount($data)) {
                        redirect(base_url('panel/reseller/cek_account/'.$_SESSION['username']));

                    }
                    else {echo 'Root passwd wrong!';}
                }


            } 

        } else { show_404(); } 
    }
    else { redirect(base_url('login/login')); }

}

在User_Model中：

public function id_ssh($id) {

    $this->db->from('sshuser');
    $this->db->where('id', $id);

    return $this->db->get()->row('');
}

public function get_user($user_id) {

    $this->db->from('users');
    $this->db->where('id', $user_id);

    return $this->db->get()->row();
}

public function renew_user_ssh($post, $id) {

    $this->db->where('Id', $id);
    return $this->db->update('sshuser', $post);
}

public function update_saldo($user, $saldo) {
    $this->db->where('username', $user);
    return $this->db->update('users', array('username' => $user, 'saldo'=>$saldo));
}