PHP/MySQL 在选择另一个时更改一个下拉菜单

Question

我希望第二个下拉列表出现在第一个下拉列表中(链接 2 个选择)。如何做到这一点，如果有人可以指导我或给我一个例子，我将不胜感激!

第一个下拉菜单:

<select name="customer">
   <option value="">--</option>
     <?php
       $sql = "SELECT * FROM ".$SETTINGS["data_table"]." GROUP BY customer ORDER BY customer";
       $sql_result = mysql_query ($sql, $connection ) or die ('request "Could not execute SQL query" '.$sql);
          while ($cust = mysql_fetch_assoc($sql_result)) {
            echo "<option value='".$cust["customer"]."'".($cust["customer"]==$_REQUEST["customer"] ? " selected" : "").">".$cust["customer"]."</option>"; } ?>
</select>

第二个下拉列表:

<select name="product">
   <option value="">--</option>
     <?php
       $sql = "SELECT * FROM ".$SETTINGS["data_table"]." GROUP BY product ORDER BY product";
       $sql_result = mysql_query ($sql, $connection ) or die ('request "Could not execute SQL query" '.$sql);
          while ($row = mysql_fetch_assoc($sql_result)) {
            echo "<option value='".$row["product"]."'".($row["product"]==$_REQUEST["product"] ? " selected" : "").">".$row["product"]."</option>"; } ?>
</select>

Answer 1

首先下拉:

<select name="customer" onchange="this.form.submit()">
   <option value="">--</option>
     <?php
       $sql = "SELECT * FROM ".$SETTINGS["data_table"]." GROUP BY customer ORDER BY customer";
       $sql_result = mysql_query ($sql, $connection ) or die ('request "Could not execute SQL query" '.$sql);
          while ($cust = mysql_fetch_assoc($sql_result)) {
            echo "<option value='".$cust["customer"]."'".($cust["customer"]==$_REQUEST["customer"] ? " selected" : "").">".$cust["customer"]."</option>"; } ?>
</select>

第二个下拉列表:

<?php if(isset($_REQUEST['customer'])){ ?>
<select name="product">
   <option value="">--</option>
     <?php
       $sql = "SELECT * FROM ".$SETTINGS["data_table"]." WHERE customer = ".$_REQUEST['customer']." GROUP BY product ORDER BY product";
       $sql_result = mysql_query ($sql, $connection ) or die ('request "Could not execute SQL query" '.$sql);
          while ($row = mysql_fetch_assoc($sql_result)) {
            echo "<option value='".$row["product"]."'".($row["product"]==$_REQUEST["product"] ? " selected" : "").">".$row["product"]."</option>"; } ?>
</select>
<?php } ?>

您可以在第二个下拉列表中添加一个 where 条件，查询将是，

$sql = "SELECT * FROM ".$SETTINGS["data_table"]." WHERE customer = ".$_REQUEST['customer']." GROUP BY product ORDER BY product";

组合代码:

<form name="demo" action="#">
     <select name="customer" onchange="this.form.submit()">
       <option value="">--</option>
         <?php
           $sql = "SELECT * FROM ".$SETTINGS["data_table"]." GROUP BY customer ORDER BY customer";
           $sql_result = mysql_query ($sql, $connection ) or die ('request "Could not execute SQL query" '.$sql);
              while ($cust = mysql_fetch_assoc($sql_result)) {
                echo "<option value='".$cust["customer"]."'".($cust["customer"]==$_REQUEST["customer"] ? " selected" : "").">".$cust["customer"]."</option>"; } ?>
    </select>

    <?php if(isset($_REQUEST['customer'])){ ?>
    <select name="product">
       <option value="">--</option>
         <?php
           $sql = "SELECT * FROM ".$SETTINGS["data_table"]." WHERE customer = ".$_REQUEST['customer']." GROUP BY product ORDER BY product";
           $sql_result = mysql_query ($sql, $connection ) or die ('request "Could not execute SQL query" '.$sql);
              while ($row = mysql_fetch_assoc($sql_result)) {
                echo "<option value='".$row["product"]."'".($row["product"]==$_REQUEST["product"] ? " selected" : "").">".$row["product"]."</option>"; } ?>
    </select>
    <?php } ?>
</form>