那个地方出错了，为什么添加不了信息？

Question

<?php

header("content-type:text/html;charset=utf-8");

$dbms = "mysql";
$dbhost = "localhost";
$dbuser = "root";
$dbpwd = "";
$dbname = "student";
$dsn = "$dbms:host=$dbhost;$dbname";
try{
   $pdo = new PDO($dsn,$dbuser,$dbpwd);
   $pdo->query("set names utf8");
   $sql = "insert into stu(uid,name,sex,age,grade,class,cre_time) values ('450000','susan','男','23岁','幼儿园','中一班',now())";    
   $row = $pdo->exec($sql);
       echo "影响了".$row."行";
}catch(PDOException $e){
   die("出错了：".$e->getMessage());
}
?>

//

stu 表结构

id int(6) 自动增量    

uid varchar(8)    

name varchar(12) NULL    

sex varchar(4) NULL    

age varchar(10) NULL    

grade varchar(10) NULL    

class varchar(6) NULL    

cre_time datetime NULL    

mod_time datetime NULL