致命錯誤：第20行不支持的操作數類型

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

我猜你的$total_credits變量$used_credits不包含數字 - 它們可能包含一些對象，不能中扣除。

檢查你的get_total_credits()和get_used_credits()方法返回;確保它們返回可用於減法運算符的值。