php无法向mysql中插入值

PHP code

conn.php<?php/* * Created on 2012-5-7 * * To change the template for this generated file go to * Window - Preferences - PHPeclipse - PHP - Code Templates */ $conn=@ mysql_connect("localhost","root","admin") or die("数据库连接失败"); mysql_select_db("bbs",$conn); mysql_query("set names 'GBK'"); //使用GBK中文编码;?>add.php<?php/* * Created on 2012-5-7 * * To change the template for this generated file go to * Window - Preferences - PHPeclipse - PHP - Code Templates * */ include("conn.php"); if($_POST['submit']){  $sql="insert into message (id,user,title,content,lastdate)" .             "values ('','$_POST[user]','$_POST[title]','$_POST[content]',now())";  mysql_query($sql);  echo "发表成功"; }?>  <form action="add.php" method="post" >   用户：<input type="text" name="user"/><br>   标题：<input type="text" name="title"/><br>   内容：<textarea name="content"></textarea><br>   <input type="submit" name="submit" value="发布留言"/>  </form>

[解决办法]
mysql_query($sql) or die(mysql_error()); //这样提示什么错误