fssy/application/api/common.php

<?php
// 接口公共方法
use think\Db;
//  更新商品库存
function update_goods_stock($goods_id,$goods_no,$num){
    $goods_info = Db::table('store_goods')
        ->field('id,spec,stock')
        ->where(['id'=>$goods_id])
        ->find();
    $spec = json_decode($goods_info['spec'],true);
    foreach ($spec as $gk=>&$gv) {
        if($gv['goods_no'] == $goods_no) {
            $spec[$gk]['store_num'] = bcsub($gv['store_num'],$num) > 0 ? bcsub($gv['store_num'],$num) : 0;
        }
    }
    $stock = $goods_info['stock']-$num >0 ? $goods_info['stock']-$num:0;
 return   Db::table('store_goods')->where(['id'=>$goods_id])->update(['spec'=>json_encode($spec),'stock'=>$stock]);
}