Detailed explanation of examples of PDO data access abstraction layer in php

<?php
//1.造PDO对象
$dsn ="mysql:dbname=mydb;host=localhost";//数据库类型:dbname=数据库名称;host=链接的ip或本机
$pdo =new PDO($dsn,"root","root");//$dsn,帐号，密码
//2.写SQL语句
$sql ="select * from info"; 
$sql ="insert into info values(&#39;004&#39;,&#39;王六&#39;,&#39;男&#39;,&#39;n007&#39;,&#39;1994-02-11&#39;)";

//3.执行SQL语句
$stm = $pdo->query($sql); //查询语句用query,返回的是结果
$arr = $pdo->exec($sql);//增删改用exec，返回的是执行的行数

//4.从PDOStatement对象里面读数据
$arr =$stm->fetch(PDO::FETCH_NUM);//默认不选为PDO::FETCH_BOTH fetch为选择一条数据
$arr = $stm->fetchAll(PDO::FETCH_BOTH);//fetchAll为全选

//事务类型:即要不全部都通过，要不全部失败，可以参考淘宝购物，必须同时满足扣款，减去库存和添加订单三项条件，缺一不可
//beginTransation 启动事务
//commit 提交事务
//rollback 回滚:返回到启动事务之前


//1.造PDO对象
$dsn ="mysql:dbname=mydb;host=localhost";
$pdo =new PDO($dsn,"root","root");

//2.将PDO的错误类型设置为异常模式
$pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);

try //尝试运行,包含从开启事务到提交事务
{
  //开启事务
  $pdo->beginTransaction();
  $sql1 = "insert into info values(&#39;004&#39;,&#39;进口&#39;,&#39;男&#39;,&#39;n008&#39;,&#39;1994-05-11&#39;)";
  $sql2 = "insert into info values(&#39;005&#39;,&#39;审核&#39;,&#39;男&#39;,&#39;n009&#39;,&#39;1994-07-11&#39;)";
  $sql3 = "insert into info values(&#39;006&#39;,&#39;姐我&#39;,&#39;男&#39;,&#39;n0010&#39;,&#39;1994-08-11&#39;)";
  
  $pdo->exec($sql1);
  $pdo->exec($sql2);
  $pdo->exec($sql3);
  
  //提交事务
  $pdo->commit();
}
  catch(Exception $e)
  {
    //回滚操作
    $pdo->rollBack();
    
  }
  //强类型语言中使用
  final
  {
    //最终执行，无论有没有异常出现，该代码都会执行
  }
?>