PHP で特定のカテゴリの製品をクエリするにはどうすればよいですか?

CREATE TABLE products (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    price DECIMAL(10, 2),
    category_id INT
);

INSERT INTO products (id, name, price, category_id) VALUES
(1, '商品1', 100.00, 1),
(2, '商品2', 150.00, 2),
(3, '商品3', 80.00, 1),
(4, '商品4', 120.00, 3),
(5, '商品5', 200.00, 2);

<?php

// 连接数据库
$servername = "localhost";
$username = "root";
$password = "root";
$dbname = "ecommerce";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("数据库连接失败: " . $conn->connect_error);
}

// 查询特定分类下的商品
$category_id = 1; // 假设这里查询分类ID为1的商品

$sql = "SELECT * FROM products WHERE category_id = $category_id";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        echo "商品ID: " . $row["id"] . " - 名称: " . $row["name"] . " - 价格: $" . $row["price"] . "<br>";
    }
} else {
    echo "未找到与该分类匹配的商品";
}

$conn->close();
?>