如何在PHP中根据特定条件为下拉菜单设置默认选择选项 - How to set a default selected option in PHP for a dropdown menu based on a specific condition?

How to set a default selected option in PHP for a dropdown menu based on a specific condition?

我有一个PHP代码，从MySQL数据库生成一个下拉菜单。下拉菜单中填充了从"目录"中检索到的选项。表格我想根据特定条件设置一个默认选择选项。例如，如果设置了$_GET['in_id']，我希望在呈现下拉菜单时默认选择与该In_id对应的选项。

下面是我用来生成下拉菜单的PHP代码:

$sql = "SELECT * FROM `inventory`";
$query = mysql_query($sql);
while ($fetch = mysql_fetch_array($query)){
    echo '<option value="'.$fetch['In_id'].'">'.$fetch['In_name'].'</option>';
}
if (isset($_GET['in_id'])){
    $in_id = $_GET['in_id'];
    $sql_in = "SELECT * FROM `inventory` WHERE In_id='$in_id'";
    $query_in = mysql_query($sql_in);
    $fetch_in = mysql_fetch_array($query_in);
}

如何修改此代码以设置基于$_GET['in_id']值的默认选择选项?

试着像下面这样改变你的while循环:

 while ($fetch = mysql_fetch_array($query)){
  $in_id = $_GET['in_id'];
  $sel = '';
  if($in_id == $fetch['In_id']){
        $sel = 'selected="selected"';
  }
  echo '<option value="'.$fetch['In_id'].'" '.$sel.'>'.$fetch['In_name'].';}