根据PHP中选择的第一个下拉列表填充第二个下拉列表

Question

我正在使用PHP和Postgresql / PostGIS数据库。我的数据库模式是这样的。

1. divname |的 DISTNAME
2. dhaka |马尼格甘杰
3. dhaka |纳拉扬甘杰市
4. dhaka |蒙什甘
5. 库尔纳|杰索尔
6. 库尔纳|库什蒂亚
7. 库尔纳|莫赫尔普

我使用以下代码

<?php
$con = pg_connect("Connection Parameter");
if (!$con)
  {
  die("Could not connect: " . pg_last_error());
  }
$divquery = "SELECT DISTINCT divname FROM union_bgd 
        ORDER  BY divname";
$distquery = "SELECT DISTINCT distname FROM union_bgd
        ORDER  BY distname";
$resultDiv = pg_query($con, $divquery); 
$resultDist = pg_query($con, $distquery);

    ?>
    Division
  <select id="division" name="division" onclick = "">
  <option value="" selected="selected">Select a Division</option>
  <?php
      while($dd1 = pg_fetch_array( $resultDiv )) 
        {

        echo '<option value= "' . $dd1['divname'] . '">' . $dd1['divname'] . '</option>';

        }

    ?>

</select></br>
District
<select id="district" name="district" onclick = "">
  <option value="" selected="selected">Select a District</option>
  <?php
      while($dd2 = pg_fetch_array( $resultDist )) 
        {

        echo '<option value= "' . $dd2['distname'] . '">' . $dd2['distname'] . '</option>';

        }

    ?>

</select>

 <?php   
pg_close($con);
?>

目前它填充下拉列表中的所有divname和distname，但我想如果选择“Dhaka”，只有dhaka下的distname将在第二个下拉列表中显示。

由于

Answer 1

中应该有where条款

$distquery = "SELECT DISTINCT distname FROM union_bgd ORDER  BY distname";

像这样编辑，

$distquery = "SELECT DISTINCT distname FROM union_bgd where divname=".$selected_dist." ORDER  BY distname";