## 代码
```
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<link href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>
<!--中间内容/start-->
<div class="wrap">
<div class="container">
<div class="row">
<div class="col-md-4 col-md-offset-4">
<h1 class="text-center">后台管理</h1>
<form class="js-ajax-form" action="{:url('public/doLogin')}" method="post">
<div class="form-group">
<input type="text" id="input_username" class="form-control" name="username"
placeholder="用户名或邮箱" title="用户名或邮箱"
value="{:cookie('admin_username')}" data-rule-required="true" data-msg-required="">
</div>
<div class="form-group">
<input type="password" id="input_password" class="form-control" name="password"
placeholder="密码" title="密码" data-rule-required="true"
data-msg-required="">
</div>
<div class="form-group">
<div style="position: relative;">
<input type="text" name="captcha" placeholder="验证码" class="form-control captcha">
<captcha height="32" width="150" font-size="18"
style="cursor: pointer;position:absolute;right:1px;top:1px;"/>
</div>
</div>
<div class="form-group">
<input type="hidden" name="redirect" value="">
<button class="btn btn-primary btn-block js-ajax-submit" type="submit" style="margin-left: 0px"
data-loadingmsg="加载中…">
登录
</button>
</div>
</form>
</div>
</div>
</div>
</div>
<!--中间内容/end-->
</body>
</html>
```
