我想保留在表单提交之前选择的特定值。但在重新加载或提交后，我没有得到以前选择的值。帮帮我！

<select name="select" class="dropbtn"  onchange="this.form.submit()">
      <?php
       include 'connect.php';
       $query="SELECT * FROM `user` WHERE id =1";
       $result=mysqli_query($link_id,$query);
        while($data = mysqli_fetch_assoc($result))
        { ?>
            <option value="<?php echo $data['user_id']; ?>"> <?php echo 
            $data['address']; ?> </option>
        <?php } ?>
      </select>
   <?php
      $id = null;
      if(isset($_POST['select']))
      {
       $id = $_POST['select'];
       echo $id; 
      }
   ?>