通过PHP提交表单后，保留下拉框中的选定选项

Question

<label for='order-number'>Order Number: </label>
<select name='orderNumber' id='order-number'>
<option></option>
<?php
// Select all order numbers
$query_orderNumber = "SELECT orderNumber FROM orders ORDER BY orderNumber ASC";
// Store them into $order_numbers
$order_numbers = mysqli_query($connection, $query_orderNumber);
while ($row = mysqli_fetch_assoc($order_numbers)) {
$num = $row['orderNumber'];
$selected = (isset($_POST['orderNumber']) && ($_POST['orderNumber']=='$num')) 
? "selected='selected'":'';
echo "<option value='$num' ". $selected. " >$num</option>";
}
?>
</select>

我用数据库中的数据创建了这个下拉列表。我想在通过PHP提交表单后保留所选的选项。但它并没有保留我选择的选项。

Answer 1

您不需要像这个那样使用'$num'

$selected = (isset($_POST['orderNumber']) && ($_POST['orderNumber']== $num)) ? "selected='selected'":'';