PHP社交站点评论功能 index页提交数据无法写入数据库无报错排查

问题背景 #

我正在开发一个社交站点，需要实现帖子下方添加评论的功能。
当我在存放所有评论逻辑的comment_frame.php页面提交评论时，数据可以正常上传写入数据库；但我从index.php页面向comment_frame.php提交评论请求时，没有任何数据写入数据库，也未返回任何错误信息，相关代码如下。

可正常运行的comment_frame.php代码 #

$post_id = $_POST['post_id'] ?? 0;

<form class='comment_frame.php' id='single_form' name='postComment<?php echo $post_id; ?>' 
    method='POST'>

    <textarea name='post_body' rows="3" placeholder='Write a comment...'></textarea>

    <input type='submit' name='postComment<?php echo $post_id; ?>' value='Post'>

</form>

if(isset($_POST['postComment' . $post_id])) {

        if (empty($_POST["post_body"])) {

            // echo "Comment can't be empty";
            echo "Comment can't be empty. <a href=".$_SERVER['HTTP_REFERER'].">Try Again</a>";
            //die() also terminates the script with display the message.
            exit();
        }

        $post_body = trim(strip_tags(filter_var($_POST['post_body'], FILTER_SANITIZE_STRING)));

        $stmt = $con->prepare("INSERT INTO comments (post_body, posted_by, posted_to, post_id) 
        VALUES (?, ?, ?, ?)");
        $stmt->bind_param("sssi", $post_body, $userLoggedIn, $posted_to, $post_id);
        $stmt->execute();

        if($posted_to != $userLoggedIn) {

            $notification = new Notification($con, $userLoggedIn);
            $notification->insertNotification($post_id, $posted_to, 'comment');
        }

            $get_commenters = $con->prepare('SELECT post_body, posted_by, posted_to, date_added 
                FROM comments WHERE post_id = ? ORDER BY date_added DESC');

            $get_commenters->bind_param("i", $post_id);
            $get_commenters->execute();
            $get_commenters->bind_result($post_body, $posted_by, $posted_to, $date_added);
            $get_commenters_result = $get_commenters->get_result();
            $notified_users = array();

            while ($row = $get_commenters_result->fetch_assoc()) {

            if($row['posted_by'] != $posted_to && $row['posted_by'] != $user_to 
                && $row['posted_by'] != $userLoggedIn && !in_array($row['posted_by'], $notified_users)) {

                $notification = new Notification($con, $userLoggedIn);
                $notification->insertNotification($post_id, $row['posted_by'], "comment_non_owner");

                array_push($notified_users, $row['posted_by']);
            }
        }
    }

故障场景相关代码 #

index.php代码

<div class='comment_div'>
    <form target='frame' class='comment_frame.php?post_id=$post_id' 
    id='comment_form' name='postComment" . $post_id . "' 
    method='POST'>
        <textarea name='post_body' placeholder='Write a comment...'></textarea>
        <input type='submit' name='postComment" . $post_id . "' value='". $post_id ."'>
    </form>
</div>

对应故障场景的comment_frame.php代码

$post_id = $_POST['post_id'] ?? 0;

if(isset($_POST['postComment' . $post_id])) {

        if (empty($_POST["post_body"])) {

            // echo "Comment can't be empty";
            echo "Comment can't be empty. <a href=".$_SERVER['HTTP_REFERER'].">Try Again</a>";
            //die() also terminates the script with display the message.
            exit();
        }

        $post_body = trim(strip_tags(filter_var($_POST['post_body'], FILTER_SANITIZE_STRING)));

        $stmt = $con->prepare("INSERT INTO comments (post_body, posted_by, posted_to, post_id) 
        VALUES (?, ?, ?, ?)");
        $stmt->bind_param("sssi", $post_body, $userLoggedIn, $posted_to, $post_id);
        $stmt->execute();

        if($posted_to != $userLoggedIn) {

            $notification = new Notification($con, $userLoggedIn);
            $notification->insertNotification($post_id, $posted_to, 'comment');
        }

            $get_commenters = $con->prepare('SELECT post_body, posted_by, posted_to, date_added 
                FROM comments WHERE post_id = ? ORDER BY date_added DESC');

            $get_commenters->bind_param("i", $post_id);
            $get_commenters->execute();
            $get_commenters->bind_result($post_body, $posted_by, $posted_to, $date_added);
            $get_commenters_result = $get_commenters->get_result();
            $notified_users = array();

            while ($row = $get_commenters_result->fetch_assoc()) {

            if($row['posted_by'] != $posted_to && $row['posted_by'] != $user_to 
                && $row['posted_by'] != $userLoggedIn && !in_array($row['posted_by'], $notified_users)) {

                $notification = new Notification($con, $userLoggedIn);
                $notification->insertNotification($post_id, $row['posted_by'], "comment_non_owner");

                array_push($notified_users, $row['posted_by']);
            }
        }
    }

故障原因 #

存在两个核心错误导致提交失效：

• 表单提交地址配置错误：index.php里的表单把请求地址写到了class属性里，没有配置action属性，表单默认会提交到当前页面index.php而不是comment_frame.php，请求根本没有送到处理逻辑页。
• post_id没有传递到后端：comment_frame.php里从$_POST拿post_id，但index.php的表单里没有任何字段传递post_id，导致$post_id始终为0，isset($_POST['postComment' . $post_id])判断直接不成立，后续逻辑全部不执行。

修复方案 #

1. 修改index.php的表单代码，补全action属性，同时新增隐藏字段传递post_id：

<div class='comment_div'>
    <!-- 新增action属性指定提交地址 -->
    <form target='frame' action='comment_frame.php' 
        id='comment_form' name='postComment<?php echo $post_id; ?>' 
        method='POST'>
        <!-- 新增隐藏字段传递post_id -->
        <input type="hidden" name="post_id" value="<?php echo $post_id; ?>">
        <textarea name='post_body' placeholder='写一条评论...'></textarea>
        <input type='submit' name='postComment<?php echo $post_id; ?>' value='发布'>
    </form>
</div>

2. 可在comment_frame.php顶部加入以下代码开启错误提示，方便后续调试：

error_reporting(E_ALL);
ini_set('display_errors', 1);

内容的提问来源于stack exchange，提问作者sir toby