$mysqli->autocommit(FALSE); //关闭自动提交功能
$sql = "UPDATE users SET money = money-300 WHERE username = ‘Mike‘";
$res1 = $mysqli->query($sql);
$res1_rows = $msyqli->affected_rows;
$sql2 = "UPDATE users SET money = money+300 WHERE username = ‘Tom‘";
$res2 = $mysqli->query($sql2);
$res2_rows = $mysqli->affected_rows;
if($res1 && $res1_rows>0 && $res2 && $res2_rows>0){
$msyqli->commit(); //提交事务
echo ‘执行成功‘;
$mysqli->autocommit(TRUE); //开启自动提交功能
else{
//事务回滚
$mysqli->rollback();
echo ‘执行失败;
}