??? ?? ???? PHP ?? ??

<?php

include ("conn.php");
$id=$_POST['id'];
$user=$_POST['user'];
$title=$_POST['title'];
$content=$_POST['content'];
if ($_POST['submit']){
  $sql="insert into message(id,user,title,content,lastdate)values('','$user','$title','$content',now())";
    mysql_query($sql);
    echo "<script>alert('提交成功！返回首頁。');location.href='add.html';</script>";
}
?>

?????? ?? ??? ????, ?? ?? ? ?? ? ??? ????, SQL ??? ???? ??? ?? ??? ID? lasdata? ?????. ??? ????

echo "<script>alert('?? ??! ? ???? ?????.'); location.href='add.html';</script>";

??? ?????. js? ???? ?? ?? ?????? ????? ??? ????.

???:

$_POST