php 并发时库存减少至小于0的解决方案



  begin();//开始一个事物处理开始
    
   $sql = "UPDATE ".$GLOBALS['a']->table('seconds_kill')."
       SET kill_stock = kill_stock - 1
       WHERE sk_id='".$sk_id."' LIMIT 1" ;
     $GLOBALS['db']->query($sql);
     
     $sql = "SELECT kill_stock ".
       " FROM ".$GLOBALS['a']->table('seconds_kill').
       " WHERE sk_id='".$sk_id."'";
     $kucun = $GLOBALS['db']->getOne($sql);
      
  if($kucun<0)
  {
   rollback();
   show_message('很抱歉，您购买的商品库存不足！ ', '返回', '', 'error');
   die();
  }else{
   
   commit();
  }

//开始
function begin()
{
        $GLOBALS['db'] -> query("set autocommit=0");//设置自动提交
        $GLOBALS['db'] -> query("begin");//事务开始
}
//提交
function commit()
{
       $GLOBALS['db'] -> query("commit");//提交
       $GLOBALS['db'] -> query("set autocommit=1");
}
//回滚
function rollback()
{
       $GLOBALS['db'] -> query("rollback");//回滚所做的数据库更改
       $GLOBALS['db'] -> query("set autocommit=1");
}