PHPで開発した多段階分類・選別機能を活用した中古リサイクルサイト

CREATE TABLE categories (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(50) NOT NULL
);

CREATE TABLE subcategories (
    id INT PRIMARY KEY AUTO_INCREMENT,
    category_id INT NOT NULL,
    name VARCHAR(50) NOT NULL,
    FOREIGN KEY (category_id) REFERENCES categories (id)
);

CREATE TABLE items (
    id INT PRIMARY KEY AUTO_INCREMENT,
    subcategory_id INT NOT NULL,
    name VARCHAR(100) NOT NULL,
    price DECIMAL(10, 2) NOT NULL,
    FOREIGN KEY (subcategory_id) REFERENCES subcategories (id)
);

<label for="category">选择分类：</label>
<select id="category" name="category">
    <option value="">请选择分类</option>
    <?php
        // 获取所有一级分类
        $query = "SELECT * FROM categories";
        $result = mysqli_query($conn, $query);
        while ($row = mysqli_fetch_assoc($result)) {
            echo '<option value="' . $row["id"] . '">' . $row["name"] . '</option>';
        }
    ?>
</select>

$(document).ready(function() {
    $("#category").change(function() {
        var categoryID = $(this).val();
        $.ajax({
            url: "get_subcategories.php",
            type: "POST",
            data: { category_id: categoryID },
            success: function(response) {
                $("#subcategory").html(response);
            }
        });
    });
});

<?php
    // 获取一级分类 ID
    $categoryID = $_POST["category_id"];

    // 获取相关的二级分类
    $query = "SELECT * FROM subcategories WHERE category_id = $categoryID";
    $result = mysqli_query($conn, $query);

    // 生成二级分类选项
    echo '<option value="">请选择二级分类</option>';
    while ($row = mysqli_fetch_assoc($result)) {
        echo '<option value="' . $row["id"] . '">' . $row["name"] . '</option>';
    }
?>

<table>
    <thead>
        <tr>
            <th>名称</th>
            <th>价格</th>
        </tr>
    </thead>
    <tbody id="item-list">
        <!-- 二手物品列表将通过 AJAX 动态加载到这里 -->
    </tbody>
</table>

$(document).ready(function() {
    $("#subcategory").change(function() {
        var subcategoryID = $(this).val();
        $.ajax({
            url: "get_items.php",
            type: "POST",
            data: { subcategory_id: subcategoryID },
            success: function(response) {
                $("#item-list").html(response);
            }
        });
    });
});

<?php
    // 获取二级分类 ID
    $subcategoryID = $_POST["subcategory_id"];

    // 获取相关的二手物品
    $query = "SELECT * FROM items WHERE subcategory_id = $subcategoryID";
    $result = mysqli_query($conn, $query);

    // 生成二手物品列表
    while ($row = mysqli_fetch_assoc($result)) {
        echo '<tr>';
        echo '<td>' . $row["name"] . '</td>';
        echo '<td>' . $row["price"] . '</td>';
        echo '</tr>';
    }
?>