请问一下php的pdo如何插入一个新字段？谢谢了！

<?php

$config = [

'user' =>'root',

'passwd' =>'root',

]

try {

$db = new PDO('mysql:host=172.17.0.1port=3306dbname=test', $config['user'], $config['passwd'])

# 新建一张表 A

$db->exec('create table if not exists A (

id int unsigned not null primary key auto_increment comment \'主键id\'

)')

# 给表 A 新增一个字段 name

$db->exec('alter table A add column name varchar(50) not NULL default \'\' comment \'名称\'')

} catch (PODException $e) {

print("Error: " . $e->getMessage())

exit()

}

mysql_connect("localhost","root","") or die("登陆数据库失败")

mysql_select_db("iPad") or die("连接数据库失败")

mysql_query("set names utf8")

$sql = "ALTER TABLE `表名` ADD `字段名` 数据类型"

mysql_query($sql)

---