如何将下拉菜单中选定的数据插入数据库中的多个表中

我假设您想根据此框中的下拉选择来选择表（意味着您有多个表jun14、dis14、jun15等）

<td><center><select name="sesi">
      <option><center>-Sila pilih-</option>
      <option value="Jun 14">Jun 2014</option>
      <option value="Dis 14">Dis 2014</option>
      <option value="Jun 15">Jun 2015</option>
      <option value="Dis 15">Dis 2015</option>
      <option value="Jun 16">Jun 2016</option>
      <option value="Dis 16">Dis 2016</option>
      <option value="Jun 17">Jun 2017</option>
      <option value="Dis 17">Dis 2017</option>
      </select>
     </td>

首先你需要像这个一样改变上面的部分

//you should remove the space and add underscore in order for your query to work
//for the if statement
<td><center><select name="sesi">
      <option><center>-Sila pilih-</option>
      <option value="jun_14">Jun 2014</option>
      <option value="dec_14">Dis 2014</option>
      <option value="Jun_15">Jun 2015</option>
      <option value="Dis_15">Dis 2015</option>
      <option value="Jun_16">Jun 2016</option>
      <option value="Dis_16">Dis 2016</option>
      <option value="Jun_17">Jun 2017</option>
      <option value="Dis_17">Dis 2017</option>
      </select>
     </td>

我去掉了值中的空格，添加了一个下划线，比如jun 14变成jun_14，dec 14变成dec_14，依此类推，

现在你的newregisterphp应该看起来像这个

 <?php
//i remove your this line assuming these lines you are connecting with your database these lines i removed
//require_once "conn.php";
 //$conn = connect();
 //   $db = connectdb();
//mysql_select_db($db,$conn) or die (mysql_error() . "'n");
        //and i added this line instead in this line i am also connecting 
//with database
    $conn=  mysqli_connect('localhost', 'root', 'yourpassword', 'yourdatabasename') 
or   die(mysqli_error($con));

    $query_usr = "select * from register_jun14";
    //$usr = mysql_query($query_usr,$conn) or die(mysql_error()."'n".$query_usr);
    $usr = mysqli_query($conn,$query_usr) or die(mysqli_error()."'n".$query_usr);
    $row_usr=mysqli_fetch_assoc($usr);
    $nama_pelajar=$_REQUEST["nama_pelajar"];
    $ic_pelajar=$_REQUEST["ic_pelajar"];
    $id_pelajar=$_REQUEST["id_pelajar"];
    $sesi=$_REQUEST["sesi"];
    $kursus=$_REQUEST["kursus"];
    $no_tel=$_REQUEST["no_tel"];
    $email=$_REQUEST["email"];

    if($sesi=="jun_14")
    {
    //assuming you have Jun14 table in your database with same field as your 
    //original  insert query in the question
        $query = "INSERT INTO  Jun14(id, nama_pelajar,ic_pelajar,id_pelajar,sesi,kursus,no_tel,email) VALUES ('','$nama_pelajar','$ic_pelajar',
    '$id_pelajar','$sesi','$kursus','$no_tel','$email')";
    $result = mysqli_query($conn,$query) or die(mysqli_error($conn));
    }
    if($sesi=="dec_14")
    {
    //assuming you have Dis14 table in your database with same field as your 
        //original insert query in the question
        $query = "INSERT INTO  Dis14(id, nama_pelajar,ic_pelajar,id_pelajar,sesi,kursus,no_tel,email) VALUES ('','$nama_pelajar','$ic_pelajar',
    '$id_pelajar','$sesi','$kursus','$no_tel','$email')";
    $result = mysqli_query($conn,$query) or die(mysqli_error($conn));
    }
if($sesi=="jun_15")
    {

//assuming you have Jun15 table in your database with same field as your 
//original insert query in the question
        $query = "INSERT INTO  Jun15(id, nama_pelajar,ic_pelajar,id_pelajar,sesi,kursus,no_tel,email) VALUES ('','$nama_pelajar','$ic_pelajar',
    '$id_pelajar','$sesi','$kursus','$no_tel','$email')";
    $result = mysqli_query($conn,$query) or die(mysqli_error($conn));
    }
    //i am leaving this your query here i dont know why you need it, may be you 
//need it 
    $query = "INSERT INTO register_jun14 ( nama_pelajar,ic_pelajar,id_pelajar,sesi,kursus,no_tel,email) VALUES ('$nama_pelajar','$ic_pelajar',
    '$id_pelajar','$sesi','$kursus','$no_tel','$email')";
    $result = mysqli_query($conn,$query) or die(mysqli_error($conn));

您可以根据下拉菜单中的值进一步编写if语句为了实现下拉菜单的目标，您可以添加任意数量的条件，我不知道为什么要运行select查询。