如何获取下拉选择值并传递给mysql查询？

Question

我需要帮助。我尝试做一些多选选项。我想获取下拉selected值并将其传递给getprodi.php上的mysql查询

这是我到目前为止所写的内容..

的index.php

    <select name="prodi" id="prodi">
            <option> --- Pilih Prodi --- </option>
            <option value="all"> --- SEMUA --- </option>
               <?php
                    $pdo = new PDO('mysql:host=localhost;dbname=dataseminar', 'root', 'pwd');
                    #Set Error Mode to ERRMODE_EXCEPTION.
                    $pdo->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
                    $stmt = $pdo->prepare('SELECT * FROM prodi');
                    $stmt->execute();
                    while($row = $stmt->fetch(PDO::FETCH_ASSOC)) 
                    {
                      if($row['idprodi'] != "")
                      {
                        echo '<option value="'.$row['idprodi'].'">'.$row['namaprodi'].'</option>';
                      }
                      else
                      {
                        echo '<option value="all">--SEMUA--</option>';
                      }
                    }
                ?>
          </select>
<div>
         NIK : 
          <select name="nik" id="nik">
            <option> --- Pilih NIK --- </option>
            <option value="all"> --- SEMUA --- </option>
               <?php
                    $pdo = new PDO('mysql:host=localhost;dbname=dataseminar', 'root', 'pwd');
                    #Set Error Mode to ERRMODE_EXCEPTION.
                    $pdo->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
                    $sql = 'SELECT * FROM dosen ORDER BY nik';
                    $stmt = $pdo->prepare($sql);
                    $stmt->execute();
                    while($row = $stmt->fetch(PDO::FETCH_ASSOC)) 
                    {
                      if($row['nik'] != "")
                      {
                        echo '<option value="'.$row['nik'].'">'.$row['nik'].' - '.$row['namalengkapgelar'].'</option>';
                      }
                    }
                ?>
          </select>
         </div><br>

如您所见，选项值来自数据库

现在，某些部分来自getprodi.php

$prodi=$_POST['prodi']; //refer to selected value?
$nik=$_POST['nik'];
try{
      $DB_con->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
      $show = $DB_con->query("SELECT s.nik, d.namalengkapgelar, p.namaprodi, s.namaseminar, s.tugas, s.tempat, s.waktu, s.sertifikat, d.idprodi 
                     FROM seminar AS s LEFT JOIN dosen as d ON s.nik = d.nik
                                       LEFT JOIN prodi as p ON d.idprodi = p.idprodi 
                     WHERE s.waktu BETWEEN '$tgl_awal' AND '$tgl_akhir' AND d.idprodi = '$prodi'");

    $show->execute();
    if($prodi == 'all' && $nik == 'All' )
    {//show data
    }
    else if ($prodi == 'all' && $nik =! 'All' )
    {//show data
    }
    else if ($nik != 'All' && $prodi != 'all' )
    {//show data
    }
   }catch (Exception $e)
   {
      echo $e->getMessage(); 
   }

我在索引上提交按钮，如果点击它将显示来自getprodi.php的表格。直到我写这个问题，我仍然混淆如何将选定的值传递给mysql查询。请帮忙。

提前谢谢你。