求TP大神帮小弟我看看，为什么不能验证登陆

<!-- 弹出登陆框 -->
<div class="theme-popover">
     <div class="theme-poptit">
          <a href="javascript:;" title="关闭" class="close">×</a>
          <h3 style="font-size:20px;">会员登陆</h3>
     </div>
     <div class="theme-popbod dform">
           <form class="theme-signin" name="loginform">
                <ol>
                     <li><strong>用户名：</strong><input class="ipt" type="text" name="username"  size="20" placeholder="手机/邮箱/用户名"/></li>
                     <li><strong>密码：</strong><input class="ipt" type="password" name="password" size="20" placeholder="请输入你的密码"/></li>
                     <li><input  id="btnEnter" class="btn btn-primary" type="submit" name="submit" value="登 录 " /></li>
                     <li style="margin-left:30%;margin-top:-12%;"><a href="">忘记密码&nbsp;&nbsp;?</a></li>
                     <li style="margin-left:-20%;margin-top:12%;"><input type="checkbox">记住账号</li>
                     <li><br/><div id="datainfo"></div></li>
                </ol>
           </form>
     </div>
</div>[code=javascript]<script type="text/javascript">
	$(function(){
		//提交表单
		$('#btnEnter').click(function()
		{
			var username=$('input[name="username"]').val();
			var password=$('input[name="password"]').val();
			//alert(password);

			$.get('__URL__/doLogin',{'username':username,'password':password},function(data)
			{
				if(data=='验证成功')
				{
					window.location='__APP__/index/index';
				}
				else if(data=='验证失败')
				{
					$('#datainfo').html("管理员登录失败.");
				}
			});

			$('input[class="boxcontent"]').blur(function()
			{
				$('#datainfo').html("");
			});
		});
	});
</script>

 //登陆验证
   public function doLogin()
   {
   	$username=$_GET['username'];
   	$password=$_GET['password'];
   	$user=M('member');
   	$where['username']=$username;
   	$where['password']=md5($password);
   	$count=$user->where($where)->count();
   	if($count)
   	{
   		$_SESSION['username']=$username;
   		echo '验证成功';
   	}
   	else
   	{
   		echo '验证失败';
   	}
   }