php检测账号密码是否匹配

<style>
 #login{width: 250px;height: 120px;background-color: aquamarine;position: fixed;top: 0px;left: 0px;right: 0px;bottom: 0px;margin: auto;padding:50px;text-align: left;}
</style>
<script type="text/javascript" src="__PUBLIC__/js/jquery-3.2.1.js"></script>
<script type="text/javascript">
function rusername(obj){
 var username=$(obj).val();
 $.post("{:U('Login/lusername')}",{username:username},function(data) {
 $("#username").html(data)
 })
}
function rpassword(obj){
 var password=$(obj).val();
 $.post("{:U('Login/lpassword')}",{username:password},function(data) {
 $("#password").html(data)
 })
}
</script>
<div id="login">
 <form action="__ACTION__" method="post">
 <p><input name="username" type="text" value="" size="25" placeholder="填写用户名" onblur="rusername(this);"/><br/><span id="username" style="font-size:12px;color:red;"></span></p>
 <p><input name="password" type="password" value="" size="25" placeholder="输入密码" onblur="rpassword(this);"/><br/><span id="password" style="font-size:12px;color:red;"></span></p>
 <p><input name="submit" type="submit" value="登录"/>
        
        
        
 <input name="submit" type="submit" value="注册"/>
 </p>
 </form>
</div>

<?php
namespace Home\Controller;
use Think\Controller;
class LoginController extends Controller {
 public function login(){
 if($_POST){
 $where['username']=$_POST['username'];
 $where['password']=md5("php100".$_POST['password']);
 $users=M('users')->where($where)->select();
 if($users){
 $_SESSION['id']=$users['id'];
 $_SESSION['user_shell']=md5($users['username'].$users['password']);
 $this->redirect('Index/index');
 }else{
 echo "<script type='text/javascript'>alert('用户名或密码错误');window.history.go(-1);</script>";
 }
 }else{
 $this->display();
 }
 }
 public function lusername(){
 $where['username']=I('username');
 $users=M('users')->where($where)->select();
 if(!$users){
 echo "用户名错误";
 }
 }
 public function lpassword(){
 $where['password']=I('password');
 $users=M('users')->where($where)->select();
 if(!$users){
 echo "密码错误";
 }
 }
}