我不知道怎么了，但是我的代码没有输出“付款金额”列
$payment_tbl = TableRegistry::get("MembershipPayment");
$payments = $payment_tbl->find();
$payments->select(['payment_total'=> $payments->func()->sum('paid_amount')]);
$this->set("payments",$payments);
，然后将其作为回显$payments->payment_total;