PHP 实现知识问答网站中的问题标记和收藏功能。

CREATE TABLE `questions` (
  `id` int(11) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  `title` varchar(255) NOT NULL,
  `content` text NOT NULL
);

CREATE TABLE `tags` (
  `id` int(11) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  `name` varchar(50) NOT NULL
);

CREATE TABLE `question_tags` (
  `question_id` int(11) UNSIGNED,
  `tag_id` int(11) UNSIGNED,
  FOREIGN KEY (`question_id`) REFERENCES `questions`(`id`) ON DELETE CASCADE,
  FOREIGN KEY (`tag_id`) REFERENCES `tags`(`id`) ON DELETE CASCADE
);

<label>标签：</label>
<input type="text" id="tag-input" name="tags" autocomplete="off">
<div id="tag-suggestions"></div>

<script>
    $(document).ready(function() {
        $('#tag-input').on('keyup', function() {
            var keyword = $(this).val();
            $('#tag-suggestions').empty();
            
            if (keyword.length > 0) {
                $.ajax({
                    url: 'tag_suggestions.php',
                    data: {keyword: keyword},
                    dataType: 'json',
                    success: function(response) {
                        if (response.length > 0) {
                            $.each(response, function(index, value) {
                                $('#tag-suggestions').append('<div class="tag-suggestion">' + value.name + '</div>');
                            });
                        }
                    }
                });
            }
        });
        
        $(document).on('click', '.tag-suggestion', function() {
            var tagName = $(this).text();
            var tagInput = $('#tag-input');
            var currentTags = tagInput.val().split(',');
            
            if ($.inArray(tagName, currentTags) === -1) {
                tagInput.val(currentTags.join(',') + ',' + tagName);
            }
            
            $('#tag-suggestions').empty();
        });
    });
</script>

<?php
$keyword = $_GET['keyword'];

// 模拟从数据库中查询标签建议
$tags = array();
if ($keyword === 'php') {
    $tags[] = array('name' => 'PHP');
    $tags[] = array('name' => 'PHP框架');
} elseif ($keyword === 'javascript') {
    $tags[] = array('name' => 'JavaScript');
    $tags[] = array('name' => 'JavaScript库');
}

echo json_encode($tags);
?>

CREATE TABLE `favorites` (
  `id` int(11) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  `user_id` int(11) UNSIGNED,
  `question_id` int(11) UNSIGNED,
  FOREIGN KEY (`user_id`) REFERENCES `users`(`id`) ON DELETE CASCADE,
  FOREIGN KEY (`question_id`) REFERENCES `questions`(`id`) ON DELETE CASCADE
);

<button class="favorite-button" data-question-id="1">收藏</button>

<script>
    $(document).ready(function() {
        $('.favorite-button').on('click', function() {
            var questionId = $(this).data('question-id');
            
            $.ajax({
                url: 'favorite_question.php',
                data: {questionId: questionId},
                success: function(response) {
                    alert(response);
                }
            });
        });
    });
</script>

<?php
$questionId = $_GET['questionId'];

// 假设当前用户已经登录，获取当前用户的ID
$userId = 1;

// 将问题ID和用户ID插入到favorites表中
$connection = new mysqli('localhost', 'username', 'password', 'database');
$statement = $connection->prepare('INSERT INTO favorites (user_id, question_id) VALUES (?, ?)');
$statement->bind_param('ii', $userId, $questionId);
$statement->execute();

if ($statement->affected_rows > 0) {
    echo '问题已收藏';
} else {
    echo '收藏失败';
}

$statement->close();
$connection->close();
?>