如何获取mysql时间戳和php当前时间之间的差异？

<?php
// 连接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MySQL时间戳
$sql = "SELECT UNIX_TIMESTAMP() AS mysql_timestamp";
$result = $conn->query($sql);
$row = $result->fetch_assoc();
$mysqlTimestamp = $row["mysql_timestamp"];

// 获取PHP当前时间戳
$phpTimestamp = time();

// 计算差异
$diff = $phpTimestamp - $mysqlTimestamp;

// 输出差异值
echo "MySQL时间戳和PHP当前时间之间的差异为：" . $diff . "秒";

// 关闭数据库连接
$conn->close();
?>