这三个东西怎么搭配使用呢

	$mysqli=new mysqli("localhost","root","123456","test");

	if($mysqli->connect_error){
		die($mysql->connect_error);
	}
	//将提交设为 false(一旦提交,无法回滚)
	$mysqli->autocommit(false);
	//保存点 ，把当前记录保存
	$sql1="update account set balance=balance-1 where id=1";
	$sql2="update account set balance=balance+1 where id=2";

	$b1=$mysqli->query($sql1);
	$b2=$mysqli->query($sql2);

	if(!$b1
------解决思路----------------------
!$b2){
		//回滚
		$mysqli->rollback();
		echo "失败--".$mysqli->error;
	}else{
		//提交
		$mysqli->commit();
		echo "成功";
	}

	$mysqli->close();