PHP动态表单处理：更新问题及多变答案的策略与实践

_________________
| id | question |
|____|__________|
|  1 |    q1    |
|____|__________|

__________________________________________
| id | answer | is_correct | question_id |
|____|________|____________|_____________|
|  1 |    a1  |     0      |      1      |
|____|________|____________|_____________|
|  2 |    a2  |     0      |      1      |
|____|________|____________|_____________|
|  3 |    a3  |     1      |      1      |
|____|________|____________|_____________|

<!-- 假设 $question 和 $answers 变量已从数据库获取 -->
<form action="update_question.php" method="POST">
    <!-- 隐藏字段用于传递问题ID -->
    <input type="hidden" name="question_id" value="<?php echo htmlspecialchars($question->id); ?>">

    <!-- 问题文本输入框 -->
    <label for="question_text">问题内容:</label>
    <input type="text" name="question_text" id="question_text" value="<?php echo htmlspecialchars($question->question); ?>" required>
    <br><br>

    <h4>答案选项:</h4>
    <div id="answers_container">
        <?php foreach ($answers as $answer): ?>
            <div class="answer-item">
                <!-- 现有答案：使用答案ID作为name属性的键 -->
                <input type="text" 
                       name="answers[<?php echo htmlspecialchars($answer->id); ?>]" 
                       value="<?php echo htmlspecialchars($answer->answer); ?>" 
                       placeholder="答案文本">
                <!-- 可以添加一个复选框来标记正确答案，其name也应包含ID -->
                <input type="checkbox" 
                       name="is_correct[<?php echo htmlspecialchars($answer->id); ?>]" 
                       <?php echo $answer->is_correct ? 'checked' : ''; ?>> 正确
                <button type="button" onclick="removeAnswer(this)">移除</button>
            </div>
        <?php endforeach; ?>
    </div>
    <br>
    <button type="button" onclick="addAnswer()">添加新答案</button>
    <br><br>
    <button type="submit">更新问题及答案</button>
</form>

<script>
    let answerCounter = 0; // 用于给新答案生成临时ID
    function addAnswer() {
        const container = document.getElementById('answers_container');
        const newAnswerDiv = document.createElement('div');
        newAnswerDiv.className = 'answer-item';
        // 新答案使用 "new_answers[]" 命名，以便在后端区分
        newAnswerDiv.innerHTML = `
            <input type="text" name="new_answers[${answerCounter++}]" value="" placeholder="新答案文本">
            <input type="checkbox" name="new_is_correct[${answerCounter - 1}]"> 正确
            <button type="button" onclick="removeAnswer(this)">移除</button>
        `;
        container.appendChild(newAnswerDiv);
    }

    function removeAnswer(button) {
        button.closest('.answer-item').remove();
        // 如果需要，可以在这里添加逻辑来标记要删除的现有答案ID
        // 例如：创建一个隐藏字段，存储所有要删除的答案ID
    }
</script>

<?php
// 假设已建立数据库连接 $pdo
// error_reporting(E_ALL);
// ini_set('display_errors', 1);

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $questionId = filter_input(INPUT_POST, 'question_id', FILTER_VALIDATE_INT);
    $questionText = filter_input(INPUT_POST, 'question_text', FILTER_SANITIZE_STRING);

    if (!$questionId || empty($questionText)) {
        // 错误处理：缺少问题ID或问题文本
        die("无效的问题ID或问题文本。");
    }

    try {
        $pdo->beginTransaction();

        // 1. 更新问题文本
        $stmt = $pdo->prepare("UPDATE questions SET question = :question WHERE id = :id");
        $stmt->execute([':question' => $questionText, ':id' => $questionId]);

        // 2. 处理现有答案
        $submittedAnswerIds = []; // 存储所有提交的答案ID (包括现有和新的)

        if (isset($_POST['answers']) && is_array($_POST['answers'])) {
            foreach ($_POST['answers'] as $answerId => $answerText) {
                $answerText = filter_var($answerText, FILTER_SANITIZE_STRING);
                $isCorrect = isset($_POST['is_correct'][$answerId]) ? 1 : 0;

                if (!empty(trim($answerText))) {
                    $stmt = $pdo->prepare("UPDATE answers SET answer = :answer, is_correct = :is_correct WHERE id = :id AND question_id = :question_id");
                    $stmt->execute([
                        ':answer' => $answerText,
                        ':is_correct' => $isCorrect,
                        ':id' => $answerId,
                        ':question_id' => $questionId
                    ]);
                    $submittedAnswerIds[] = $answerId;
                } else {
                    // 如果现有答案文本被清空，则视为删除该答案
                    $stmt = $pdo->prepare("DELETE FROM answers WHERE id = :id AND question_id = :question_id");
                    $stmt->execute([':id' => $answerId, ':question_id' => $questionId]);
                }
            }
        }

        // 3. 处理新答案
        if (isset($_POST['new_answers']) && is_array($_POST['new_answers'])) {
            foreach ($_POST['new_answers'] as $tempKey => $newAnswerText) {
                $newAnswerText = filter_var($newAnswerText, FILTER_SANITIZE_STRING);
                $newIsCorrect = isset($_POST['new_is_correct'][$tempKey]) ? 1 : 0;

                if (!empty(trim($newAnswerText))) {
                    $stmt = $pdo->prepare("INSERT INTO answers (question_id, answer, is_correct) VALUES (:question_id, :answer, :is_correct)");
                    $stmt->execute([
                        ':question_id' => $questionId,
                        ':answer' => $newAnswerText,
                        ':is_correct' => $newIsCorrect
                    ]);
                    // 对于新插入的答案，我们没有立即获取其ID，但它们已经关联到问题
                }
            }
        }

        // 4. (可选) 处理被删除的答案
        // 如果需要精确处理删除，需要从数据库中获取原始答案ID列表，
        // 然后与 $submittedAnswerIds 进行比较，找出差异并执行删除。
        // 例如：
        /*
        $originalAnswerIds = []; // 从数据库获取当前问题的所有答案ID
        $stmt = $pdo->prepare("SELECT id FROM answers WHERE question_id = :question_id");
        $stmt->execute([':question_id' => $questionId]);
        while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
            $originalAnswerIds[] = $row['id'];
        }

        $answersToDelete = array_diff($originalAnswerIds, $submittedAnswerIds);
        foreach ($answersToDelete as $deleteId) {
            $stmt = $pdo->prepare("DELETE FROM answers WHERE id = :id AND question_id = :question_id");
            $stmt->execute([':id' => $deleteId, ':question_id' => $questionId]);
        }
        */
        // 上述代码中，如果现有答案文本被清空，已经视为删除，所以这一步可能不是必需的，
        // 取决于前端删除逻辑和用户期望。

        $pdo->commit();
        echo "问题及答案更新成功！";
        // 重定向到编辑页面或详情页面
        // header("Location: edit_question.php?id=" . $questionId);
        // exit();

    } catch (PDOException $e) {
        $pdo->rollBack();
        die("数据库操作失败: " . $e->getMessage());
    }
} else {
    die("无效的请求方法。");
}
?>