如何把循环中的内容逐个相加

Question

for($counter=$i; $counter>=1; $counter--){
$weight="weight_$counter";
$single_price="single_price_$counter";
$total_price="$_POST[$weight]"*"$_POST[$single_price]";
$id="id_$counter";
}
$big_total_price=$total_price+.......;
大概意思就是把每一次for循环中的$total_price进行相加，最后得出来一个总的$big_total_price，这样的话应该怎么写？

Answer 1

$big_total_price=0;
for($counter=$i; $counter>=1; $counter--){
            $weight="weight_$counter";
            $single_price="single_price_$counter";
            $big_total_price+="$_POST[$weight]"*"$_POST[$single_price]";
            $id="id_$counter";
        }

Answer 2

循环外定义一个变量初始值为0
$total = 0;
循环体内一直加$total_price
$total += $total_price;