PHP学习：php+Mysqli利用事务处理转账问题实例

<?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(); 
?>