PHP编程：php利用事务处理转账问题

<?php 
 header("Content-type:text/html; charset=utf-8"); 
  
 $mysqli = new mysqli("localhost","root","064319","php"); 
 $mysqli->set_charset("utf8"); 
  
 if($mysqli->connect_errno) { 
  die('数据库连接失败'.$mysqli->connect_error); 
 } 
  
 $mysqli->autocommit(false); //自动提交模式设为false 
 $flag = true; //事务是否成功执行的标志 
  
 $query = "update account set balance=balance-1000 where id=3"; 
 $result = $mysqli->query($query); 
 $affected_count = $mysqli->affected_rows; 
 if(!result || $affected_count == 0) { //失败 
  $flag = false;  
 } 
  
 $query = "update account set balance=balance+1000 where id=2"; 
 $result = $mysqli->query($query); 
 $affected_count = $mysqli->affected_rows; 
 if(!$result || $affected_count == 0) { 
  $flag = false; 
 } 
  
 if($flag) { 
  $mysqli->commit(); 
  echo '转账成功'; 
 } else { 
  $mysqli->rollback(); 
  echo '转账失败'; 
 } 
  
 $mysqli->autocommit(true); //重新设置事务为自动提交 
 $mysqli->close(); 
?>

<?php 
 try{ 
 $pdo=new PDO("mysql:host=localhost;dbname=psp",""); 
 $pdo->exec("set names utf8"); 
 $pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);//设置异常处理模式 
 $pdo->setAttribute(PDO::ATTR_AUTOCOMMIT,0);//关闭自动提交 
 }catch(PDOException $e){ 
 echo "数据库连接失败"; 
 exit; 
 } 
 
 try{ 
 $age=10; 
 $pdo->beginTransaction();//开始事务 
 $affected_rows1=$pdo->exec("update kfry set k_age=k_age+{$age} where k_name='user1'"); 
 $affected_rows2=$pdo->exec("update kfry set k_age=k_age-{$age} where k_name='user2'");//随意更改使之执行成功或失败 
 /* if($affected_rows1&&$affected_rows2) 
 { 
 $pdo->commit(); 
 echo "操作成功"; 
 }else{ 
 $pdo->rollback(); 
 } */
 if(!$affected_rows1) 
 throw new PDOException("加入错误"); 
 if(!$affected_rows2) 
 throw new PDOException("减少错误"); 
 echo "操作成功"; 
 $pdo->commit();//如果执行到此处前面两个更新sql语句执行成功,整个事务执行成功 
 }catch(PDOException $e){ 
 echo "操作失败：".$e->getMessage(); 
 $pdo->rollback();//执行事务中的语句出了问题,整个事务全部撤销 
 } 
 $pdo->setAttribute(PDO::ATTR_AUTOCOMMIT,1); 
 //测试是否成功 
 echo "n操作结果为:n"; 
 $sql="select * from kfry"; 
 $result=$pdo->query($sql); 
 foreach($result as $v) 
 { 
 echo $v['k_name']." ".$v['k_age']."n"; 
 } 
?>