Php 如何在laravel控制器中对以下数组中的值求和？

我有一个laravel项目，我想把这3个值加在一个变量中，然后存储在b中，我怎么做

$benefit = Order::where('ot_id', $order->ot_id)->sum('ot_benefit');
$a_ben = Order::where('ot_id', $order->ot_id)->sum('subtotal') - sum('ot_benefit') - sum('discount');
$updateData = ['ben_earned' => $benefit , 'a_ben' => $a_ben];

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此查询在求和函数上创建错误

问题在第二行。不能像调用3次那样调用sum函数

$benefit = Order::where('ot_id', $order->ot_id)->sum('ot_benefit'); 

$subtotal = Order::where('ot_id', $order->ot_id)->sum('subtotal'); 

$discount = Order::where('ot_id', $order->ot_id)->sum('discount'); 

$a_ben = $ot_benefit - $subtotal - $discount;

$updateData = ['ben_earned' => $benefit , 'a_ben' => $a_ben];

然后：

$total = $order->st + $order->ot - $order->discount;

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哦，谢谢你

$total = $order->st + $order->ot - $order->discount;