如何将PHP HTTP_USER_AGENT保存到MySQL字段

CREATE TABLE user_agents (
    id INT AUTO_INCREMENT PRIMARY KEY,
    user_agent VARCHAR(255)
);

// 连接到MySQL数据库
$servername = "数据库服务器地址";
$username = "数据库用户名";
$password = "数据库密码";
$dbname = "数据库名称";

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

// 获取HTTP_USER_AGENT的值
$user_agent = $_SERVER['HTTP_USER_AGENT'];

// 将HTTP_USER_AGENT的值插入到数据库中
$sql = "INSERT INTO user_agents (user_agent) VALUES ('$user_agent')";
if ($conn->query($sql) === TRUE) {
    echo "HTTP_USER_AGENT保存成功";
} else {
    echo "保存失败: " . $conn->error;
}

// 关闭数据库连接
$conn->close();