phpで簡単なチャット機能を実装

CREATE TABLE `guanhui`.`message` ( 
    `id` INT(10) NOT NULL AUTO_INCREMENT COMMENT '消息ID' , 
    `content` VARCHAR(255) NOT NULL COMMENT '消息内容' , 
    `sender` VARCHAR(60) NOT NULL COMMENT '发送者' , 
    `send_time` INT(10) NOT NULL COMMENT '发送时间' ,
     PRIMARY KEY (`id`)
 ) ENGINE = MyISAM;

$con = mysql_connect("localhost","","");
if (!$con) {
    die('Could not connect: ' . mysql_error());
}
mysql_select_db("chat", $con);
mysql_query("set names 'utf8'");            
$sql = "SELECT * FROM  `message`";
$result = mysql_query($sql);
if(isset($result)){
    json_encode(array(
        'code' => 0,
        'msg' => 'OK',
        'data' => mysql_fetch_array($result, MYSQL_ASSOC)
    ))
} else {
    json_encode(array(
        'code' => 0,
        'msg' => '聊天信息为空！'
    ))
}

setInterval(function(){

    $.get('/get_message_list.php', function(data){

        $(data).each(function(value, item){
            $('#message_list').append('来自：' + data.sender + '的消息：' + data.message + '发送时间：', data.send_time);
        });

    });

}, 600);

$send_time = date('Y-m-d H:i:s',time());;
$send = $_POST['sender'];
$content = $_POST['content'];
$con = mysql_connect("localhost","","");
if (!$con) {
  die('Could not connect: ' . mysql_error());
}
mysql_select_db("ing", $con);
mysql_query("set names 'utf8'");
$insert="INSERT INTO  `chat` (`id` ,`sender` ,`content` ,`send_time`) VALUES (NULL ,  '$sender',  '$content',  '$send_time')";
$result = mysql_query($insert);