致命错误：第 20 行不支持的操作数类型

Question

第 20 行：$this->data['available_credits'] = $total_credits - $used_credits;

    function index()   {
    $user_id = $this->session->userdata('user_id');
    $this->data['credits'] = $this->credit_m->get_credit_details($user_id);
    $total_credits = $this->data['total_credits'] = $this->credit_m->get_total_credits($user_id);
    $used_credits = $this->data['used_credits'] = $this->credit_m->get_used_credits($user_id);
    $this->data['available_credits'] = $total_credits - $used_credits;
    $this->template->build('credits_view',$this->data);
}

Answer 1

我猜测您的 $total_credits 变量 $used_credits 不包含数字 - 它们可能包含一些无法减去的对象。

检查您的 get_total_credits() 和 get_used_credits() 方法返回的内容；确保它们返回可与减法运算符一起使用的值。