谁帮忙写个PHP代码，代码中有用户名和密码在页面输入正确就登陆到一个页面

<?php
session_start();
$coon_ = "localhost";
$name_ = "root";
$password_="root";
$error_ = "无法连接数据库1，请重来";
$conn=mysql_connect($coon_,$name_,$password_) or die($error_);
mysql_select_db("abc")
or die($error_);
mysql_query("SET NAMES 'gbk'");//解决汉字

$row = mysql_fetch_assoc(mysql_query(" SELECT pass,qx,sex FROM users where name = '$username' and pass = '$pass'"));
$dl_mima=$row[pass];$dl_qx=$row[qx];$dl_sex=$row[sex];
if($dl_mima=="")
{
echo "<script>alert(\"您输入的用户名或者密码错误，请重新输入！\")</script>";
echo "<form id=\"form2\" name=\"form2\" method=\"post\" action=\"\">
<table width=\"452\" height=\"148\" border=\"1\" align=&#