php与数据库相关重要有关问题求解答 _PHP

php与数据库相关重要问题求解答
各位前辈高人，我在login.html中点击登录后直接转向userController.php,并且不显示任何东西，我的目的是验证登录成功后直接跳到mian.html 不成功则跳到error.html中，可是不成功，请问我哪里错了，还有一个问题就是登录成功后怎么吧登录者的信息传给mian.html?谢谢了

PHP code

 
login.html
<html>
<head>
    <title>用户系统登录</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> 
</head>
<body>
<form name="loginfrom" action="userController.php?flag=login"method="POST">
<table  background="resource/background.jpg" width= "100%"  height= "100%"   border= "0 ">
<tr>
<td align= "center "   valign= "middle ">
    <table align="center">
        <tr>
            <th>角色</th>
            <td><input type="radio" name="account"  value="admin" checked>管理员
                <input type="radio" name="account" value="teacher">教师
                <input type="radio" name="account"  value="student">学生
            </td>
        <tr>
            <th>用户名</th>
            <td><input type="text" name="user_name" ></td>
        </tr>
        <tr>
            <th>密码</th>
            <td><input type="password" name="user_password" ></td>
        </tr>
        <tr>
            <td align="right" colspan="2"><a href="register.html">新用户注册</a><button type="submit" name="submit">登录</button></td>
        </tr>
    </table>
</td>
</tr>
</table>
</form>
</body>
</html>

PHP code


dbconn.class.php
<?php
    class DBconn{
        private static $db_host="localhost";
        private static $db_user="root";
        private static $db_password="linux";
        private static $db_name="sharewebDb";
        private static $connection;
        static function getConn(){
            $connection=new mysqli($db_host,$db_user,password,$db_name);
            return $connection;
        }    
    }
?>

PHP code


userModel.php
<?php 
include("dbconn.class,php");
class userModel{
    function checklogin($userid,$userpwd,$useraccount){
        $mysqli=DBconn::getConn();
        $result='';
        switch($useraccount){
        case "teacher":{
                $sql="select t_id,t_name,t_dep from ter_info where t_id=? and t_pwd=?";
                $result=$mysqli->prepare($sql);:
                $result->bind_param("ss",$user_id,$user_password);
                $user_id=$userid;
                $user_password=$userpwd;
                $result->execute();break;
                }
        case "student":{
                $sql="select s_id,s_name,s_dep from stu_info where s_id=? ands_pwd=?";
                $result=$mysqli->prepare($sql);
                $result->bind_param("ss",$user_id,$user_password);
                $user_id=$userid;
                $user_password=$userpwd;
                $result->execute();break;
                }
        }
        $result->bind_result($user_id,$user_name,$user_dep);
        while($result->fetch()){
            $userlist=array(
                'user_id'=>$user_id,
                'user_name'=>$user_name,
                'user_dep'=>$user_dep
            );        
        }
        $result->close();
        $mysqli->close();
        return userlist;
    }
?>