PHP学习：简单实现PHP留言板功能

PHP实例
<div class="continer" >
  <div class="head" style="background-color:rgb(217,237,247);height:50px;vertical-align:middle"><h2 style="color: rgb(81,117,114)">PHP留言本</h2></div>
  <div class="body">
    <volist name="guestbook" id="vo">
      <div class="panel">
        <div class="panel-head" style="background-color: rgb(223,240,216)">
          <span class="nickname" style="color: rgb(104,148,99)">留言者: {$vo.nickname}</span>
          <span style="color: rgb(104,148,99)">|</span>
          <span class="email" style="color: rgb(104,148,99)">邮箱: {$vo.email}</span>
          <span class="time" style="float: right;color: rgb(104,148,99)">时间: {$vo.replytime}</span>
        </div>
        <div class="panel-body">
          <span class="content">内容: {$vo.content}</span>
          <span class="time" style="float: right">{$vo.id}楼</span>
        </div>
      </div>
    </volist>
  </div>
  <div class="foot">
    <form method="post">
      <div class="panel" style="background-color: rgb(245,245,245)">
        <div class="panel-body" style="padding:30px; width: 20%">
          <div class="form-group">
            <div class="field field-icon-right">
              <input id="nickname" type="text" class="input" name="nickname" placeholder="游客姓名"/>
            </div>
          </div>
          <div class="form-group">
            <div class="field field-icon-right">
              <input type="text" id="content" class="input" name="content" placeholder="留言内容"/>
            </div>
          </div>
          <div class="form-group">
            <span></span>
            <span class="field">
              <input type="text" id="email" class="input" name="email" placeholder="Email"/>
            </span>
          </div>
          <div class="form-group">
            <span><button name="liuyan">留言</button></span>
            <span><button name="restart" onclick="clearDefaultText(this)">重置</button></span>
          </div>
        </div>
      </div>
    </form>
  </div>
</div>
<script>
function clearDefaultText(){
  var nickname = document.getElementById('nickname');
  var content = document.getElementById('content');
  var email = document.getElementById('email');
  nickname.value="";
  content.value="";
  email.value="";
}
</script>

PHP实例
public function hierarchicalauthority(){
 if(isset($_POST['liuyan']))
 {
  $data['nickname']=$_POST['nickname'];
  $data['content']=$_POST['content'];
  $data['email']=$_POST['email'];
  $data['status']=1;
  $data['replytime']=date('Y-m-d H:i:s',time());
  // print_r($data);die();
  $user=M('daili_liuyan_guestbook');
  $maxid=$user->max('id');
  $data['id']=$maxid+1;
  $user->add($data);
 // print_r($_POST);die();
 }
 $guestbook = D('daili_liuyan_guestbook')->select();
 $this->assign('guestbook',$guestbook);
 $this->display();
}