php - 无法从 while 循环中回显 html 的值

Question

我想回显所选的父值。但我收到错误通知:未定义索引:那么我如何echo选定的父值呢？我做错了什么？

$q = mysql_query("SELECT * FROM menu");
    echo '<form action="" method="post">
      Menu name:<input type="text" name="mname"><br>
      <select>';
    while ($row = mysql_fetch_array($q)) {
        $menu_name = $row['menu_name'];

    echo '<option value="'.$menu_name.'">'.$menu_name.'</option>';
    }
    echo '</select><br>
      <input type="submit" name="submit" value="Add Menu">
    </form>';



    if (isset($_POST['submit'])) {
        echo $mname = $_POST['mname'];
        echo $parent = $_POST[$menu_name];
    }

Answer 1

向选择框添加名称，并通过名称获取选择框的值。更新的代码:-

$q = mysql_query("SELECT * FROM menu");
echo '<form action="" method="post">
  Menu name:<input type="text" name="mname"><br>
  <select name="menu_name">';
while ($row = mysql_fetch_array($q)) {
    $menu_name = $row['menu_name'];

echo '<option value="'.$menu_name.'">'.$menu_name.'</option>';
}
echo '</select><br>
  <input type="submit" name="submit" value="Add Menu">
</form>';



if (isset($_POST['submit'])) {
    echo $mname = $_POST['mname'];
    echo $parent = $_POST['menu_name'];
}