MongoDB和PHP错误通知：未定义索引：变量

我正在尝试创建一个表单，在其中我将使用MongoDB和PHP添加数据、删除和更新。 但现在我被更新部分卡住了。 我一单击更新按钮，它就会抛出以下错误并删除所有以前存在的记录数据

这是update.php文件

<?php 

require 'vendor/autoload.php';
$conn=new MongoDB\Client("mongodb://localhost:27017");
$db=$conn->project;
$collection=$db->notes;
if(!empty($_GET['id'])){
    $id = $_GET['id'];
    $id =new  MongoDB\BSON\ObjectId($id);
    $docs=$collection->findOne(array('_id'=>$id));
    ?>

    <?php 

    try{
        if(isset($_POST['update'])){
        $collection->updateOne(
            array('_id' => $id),
            array(
                '$set' => array(
                    'author' => $_POST['author'],
                    'subject' => $_POST['subject'],
                    'title' => $_POST['title'],
                    'notes' => $_POST['notes'],
                    'difficulty' => $_POST['difficulty'],
                    'rel_topic' => $_POST['rel_topic']
                )
            )
            
        );
        echo " Updated successfully";
        // header("location:real.php");
    }
    }
    catch(Exception $e){
        echo 'Error '.$e->getMessage();
    }
    
}

    
?>
    <form method="post">
        <p>ID: <?php echo $docs['_id']?></p>
        Author:<input type='text' id='author' value='<?php echo $docs['author']?>'/><br>
        Title:<input type='text' id='title' value='<?php echo $docs['title']?>'/><br>
        Subject:<input type='text' id='subject' value='<?php echo $docs['subject']?>'/><br>
        Notes:<input type='text' id='notes' value='<?php echo $docs['notes']?>'/><br>
        Difficulty:<input type='text' id='difficulty' value='<?php echo $docs['difficulty']?>'/><br>
        Related Topic:<input type='text' id='rel_topic' value='<?php echo $docs['rel_topic']?>'/><br>
        <button type="submit" name="update">Update</button>
    </form>

请帮帮我

您的输入必须具有“name”属性

 Author:<input type='text' name='author' value='<?php echo $docs['author']?>'/><br>

2种方式：

在一次isset通话中检查所有按键：

if（isset（$\u POST['author']，$\u POST['subject']）{

创建循环并在缺少键时引发异常：

foreach（['author'，'subject']作为$key）{
如果（isset（$\u POST[$key]））{
抛出新异常（“缺少键“$Key”）；
}
}

在if条件之前，在顶部将docs变量初始化为空数组-

$docs = [];

然后，将其替换为html-

<form method="post">
<p>ID: <?php echo $docs['_id'] ?? ''; ?></p>
Author:<input type='text' id='author' value='<?php echo $docs['author'] ?? ''; ?>'/><br>
Title:<input type='text' id='title' value='<?php echo $docs['title'] ?? ''; ?>'/><br>
Subject:<input type='text' id='subject' value='<?php echo $docs['subject'] ?? ''; ?>'/><br>
Notes:<input type='text' id='notes' value='<?php echo $docs['notes'] ?? ''; ?>'/><br>
Difficulty:<input type='text' id='difficulty' value='<?php echo $docs['difficulty'] ?? ''; ?>'/><br>
Related Topic:<input type='text' id='rel_topic' value='<?php echo $docs['rel_topic'] ?? ''; ?>'/><br>
<button type="submit" name="update">Update</button>
</form>

身份证：

作者：这回答了你的问题吗？很高兴知道，你能接受这个答案吗？
$docs = [];

<form method="post">
<p>ID: <?php echo $docs['_id'] ?? ''; ?></p>
Author:<input type='text' id='author' value='<?php echo $docs['author'] ?? ''; ?>'/><br>
Title:<input type='text' id='title' value='<?php echo $docs['title'] ?? ''; ?>'/><br>
Subject:<input type='text' id='subject' value='<?php echo $docs['subject'] ?? ''; ?>'/><br>
Notes:<input type='text' id='notes' value='<?php echo $docs['notes'] ?? ''; ?>'/><br>
Difficulty:<input type='text' id='difficulty' value='<?php echo $docs['difficulty'] ?? ''; ?>'/><br>
Related Topic:<input type='text' id='rel_topic' value='<?php echo $docs['rel_topic'] ?? ''; ?>'/><br>
<button type="submit" name="update">Update</button>
</form>