php - 无法弄清楚为什么我得到一段代码的“未定义索引”而不是另一段

Question

我有几个要从中提取数据的“多个”选择框。前两个工作正常，但是当我到达第三个时，要么isset($_POST('name'))返回 false，要么，如果我将其取出，我会收到“未定义索引”通知。

我尝试复制粘贴代码并更改名称、重新键入、更改 HTML 和 php 中的变量名称。现在我正用头撞键盘。

的HTML：

<div class = "streamingPlatform">
        <label> <span class = "headings"> Streaming Platform </span>
            <select name = "platform[]" multiple = "multiple" size = "3">
                <option value = "amazon"> Amazon Prime </option>
                <option value = "apple"> Apple TV+ </option>
                <option value = "crunchy"> CrunchyRoll </option>
                <option value = "disney"> Disney+ </option>
                <option value = "hbo"> HBO Now </option>
                <option value = "hulu"> Hulu </option>
                <option value = "netflix"> Netflix </option>
                <option value = "showtime"> Showtime </option>
                <option value = "starz"> Starz </option>
            </select>
        </label>
        </div>
        <div class = "rating">
        <label> <span class = "headings"> Rating </span>
            <select name = "mpaa[]" multiple = "multiple" size = "3">
                <option value = "g"> G </option>
                <option value = "pg"> PG </option>
                <option value = "pg13"> PG-13 </option>
                <option value = "r"> R </option>
                <option value = "nc17"> NC-17 </option>
            </select>
        </label>
        </div>

php：

if(isset($_POST['platform']))   
    $platform = $_POST['platform'];
  if(isset($_POST['mpaa']))
      $mpaa = $_POST['mpaa'];

目前 $platform 将返回值，$mpaa 不会。如果我在最后一行收到“未定义索引”通知之前删除了if(isset($_POST['mpaa']))from 。$mpaa = $_POST['mpaa'];

提交给 php 的 HTML：

<form method="POST"  action="simpleSearch.php">

        <div class = "searchBar">
        <p>Search Movies: 
        <input type="text" name="movie_name" />
        <input type = "submit" value = "Search" />

标签： phphtmlundefined-index