留言板 出錯了 就是找不到錯誤在哪裡 頭痛

Question

add.php檔案內容

<?php
//匯入連線資料庫檔案
include ('conn.php');
//偵測使用者是否提交按鈕
if(isset($_POST['submit'])){
         $id=$_POST['id'];
      1 $title=$_POST['title'];
         $content=$_POST['content'];
    $sql="insert into message(id,user,title,content,lastdate)value$sql="insert into message(id,user,title,content,lastdate)value$sql="insert into message(id,user,title,content,lastdate)value$sql' ,'$user','$title','$content',now())";
    mysqli_query($conn,$sql);
//    echo "<script>alert('新增成功');history.go(-1)</script>";
echo"<script>alert('留言成功');location.href='liu.html'</script>";
}else{
    echo "失敗";
}
?>

liu.html內容

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