php面向对象2

<form action="lianxi3.php" method="post">
<input type="submit" name="submit2" value="登录">
</form>
<?php
if(isset($_POST['submit'])){
$huifu = $_POST['huifu'];
$conn = mysql_connect("localhost","root","") or die("链接数据库失败");
mysql_select_db("xiangmu");
mysql_query("set names 'utf8'");
$sql = "INSERT INTO `huitie`(`id`, `huifren`, `huitie`, `fabiaohuifu`) VALUES (null,null,null,'$huifu')";

mysql_query($sql);