表使用php循环连接子类别

<?php
// 连接数据库
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 查询父类别
$sql = "SELECT * FROM categories WHERE parent_id IS NULL";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        echo "父类别：" . $row["name"] . "<br>";

        // 查询子类别
        $parent_id = $row["id"];
        $sql_sub = "SELECT * FROM categories WHERE parent_id = $parent_id";
        $result_sub = $conn->query($sql_sub);

        if ($result_sub->num_rows > 0) {
            while ($row_sub = $result_sub->fetch_assoc()) {
                echo "子类别：" . $row_sub["name"] . "<br>";
            }
        } else {
            echo "暂无子类别";
        }
    }
} else {
    echo "暂无父类别";
}

$conn->close();
?>