PHP如何实现留言板功能

CREATE TABLE `guanhui`.`message` (
  `id` INT(10) NOT NULL AUTO_INCREMENT COMMENT '消息ID' ,
  `sender` VARCHAR(60) NOT NULL COMMENT '发送者' ,
  `content` TEXT NOT NULL COMMENT '消息内容' ,
  `send_time` INT(10) UNSIGNED NOT NULL DEFAULT '0' COMMENT '发送时间' ,
  PRIMARY KEY (`id`)
) ENGINE = MyISAM;

<form action="./send_message.php" method="POST">


  <input type="text" name="sender" placeholder="你的昵称">
  <textarea rows="4" name="content" placeholder="留言内容"></textarea>
  <button type="submit">发送</button>
</form>

<?php
//链接数据库
$conn = mysql_connect("loclhost:3306","root","root"); 
//判断错误函数
if(!$conn){
   die(mysql_error());
}
//选择数据库
mysql_query("use message",$conn);
//设定字符集编码
mysql_query("set names utf8",$conn);
//查询语句
$sql = "select * from message";
//执行语句
$res = mysql_query($sql);
//建立一个空数组
$data = array();
//执行循环
while($row = mysql_fetch_assoc($res)){
     $data[] = $row;
}
?>
<table>
  <tr>
    <th>ID</th>
    <th>Name</th>
    <th>Sender</th>
    <th class="content">Content</th>
    <th>操作</th>
  </tr>
  <?php foreach($data as $k=>$v){?>  
    <tr>
      <td><?=$v['id']?></td>
      <td><?=$v['name']?></td>
      <td><?=$v['sender']?></td>
      <td><?=$v['content']?></td>
      <td>
      <a href="./update.php?id=<?=$v['id']?>">修改</a>
      <a href="./del.php?id=<?=$v['id']?>">删除</a>
      </td>
    </tr>
  <?php }?>
<table>

<?php
//链接数据库
$conn = mysql_connect("loclhost:3306","root","root"); 
//判断错误函数
if(!$conn){
   die(mysql_error());
}
//选择数据库
mysql_query("use message",$conn);
//设定字符集编码
mysql_query("set names utf8",$conn);
 
//获取表单值
$name = $_POST['name'];
$sender = $_POST['sender'];
$content =$_POST['content'];
//插入数据库语句
$sql = "insert into message(name,sender,content)values('$name','$sender','$content')";
//执行数据
$res = mysql_query($sql);
//判断结果
if($res){
    echo "增加成功";
}else{
    die("增加失败".mysql_error());
}