包含所有发票ID的下拉菜单。B下拉菜单，其中填充了所有项目描述。以下是我的代码，只有一个下拉菜单显示，我不知道如何显示这两个。
<html>
<head>
<title>3-invoice-item.php</title>
<link href="main.css" rel="stylesheet">
</head>
<body>
<div class="container">
<h3>Select invoice_id and item_description and enter quantity:</h3>
<form method="post" action="new 4.php">
<div><label for="invoice">invoice_id </label><select name="invoice"><?php
include "config.php";
$c = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME) or die("Connection failed: " . mysqli_connect_error());
$query = "SELECT invoice_id
from invoice";
$results = mysqli_query($c, $query) or die("Query failed: " . mysqli_error($c));
while ($result = mysqli_fetch_array($results)) {
echo "<option>" . $result['invoice_id'] . "</option>";
}
$query = "SELECT item_description
from item";
$results = mysqli_query($c, $query) or die("Query failed: " . mysqli_error($c));
while ($result = mysqli_fetch_array($results)) {
echo "<option>" . $result['invoice_id'] . "</option>";
}
mysqli_free_result($results);
mysqli_close($c);
?></select></div>
<div><label for="quantity">quantity: </label><input type="text" name="quantity"></div>
<div><input type="submit" name="submit"></div>
</form>
</div>
</body>
</html>
没有创建第二个下拉列表的代码。尝试在第一个while循环结束后添加此项。
echo "</select>";
echo "<select name='my_dropdown'>";