我会说清楚的。所以当我在select下拉列表中选择一个选项或值时，我只想在文本框中显示我的所有数据，但我不知道怎么做。我在选择下拉列表中选择了一个值之后，似乎什么都没有显示。谢谢！
这是我的数据库的样子

另外，我在selectbox上传递金额，因此当我单击例如500时，文本框将填充其值，如 pin , code 以及表中的其他字段
这是我的页面的样子

<form action="" method="POST">
            <div class="row  col-md-4">

            <?php 

            $connection = mysqli_connect("localhost","root","");
            $db = mysqli_select_db($connection, 'qrproject');
            ?>

              <label>Amount</label>

              <select class="form-control validate" name="id">
                <?php 
                  $sql = mysqli_query($connection, "SELECT amount FROM scratch_cards GROUP BY `amount`");
                  while ($row = $sql->fetch_assoc()){
                  echo "<option value=\"amnt1\">" . $row['amount'] . "</option>";
                  }
                ?>
              </select>
               <br>
            <input type="submit" class="form-control btn-warning" name="search" value="Search Data"></input><br>

            <?php
            if(isset($_POST['search']))
            {
              $id = $_POST['id'];

              $query = "SELECT * FROM scratch_cards WHERE amount='$id' ORDER BY RAND() LIMIT 1";
              $query_run = mysqli_query($connection, $query);

              if($row = mysqli_fetch_array($query_run))
              {
                ?>
                <form action="" method="POST">

                <input type="text" name="code" value="<?php echo $row['code'] ?>" class="form-control validate" id="mapo">

                   <input type="text" name="pin" value="<?php echo $row['pin'] ?>" class="form-control validate" id="mact">

                   <input type="text" name="txtstatus" value="<?php echo $row['status'] ?>" class="validate form-control" id="soluong">

                <input type="date" name="card_expiration" value="<?php echo $row['card_expiration'] ?>" class="validate form-control" id="cardex">

                  <input type="number" name="card_validity" value="<?php echo $row['card_validity'] ?>" class="validate form-control" id="cardval">

                  <input type="hidden" name="success" class="validate form-control" id="success" value="SUCCESS">

                </form>
                <?php 
              }
            }
             ?>   
        </form>