PHP fatal error : Call to a member function diff() on a non-object in. .. 比较数据库中的日期时间

Question

我试图比较两个不同的日期时间并找出差异。

我在尝试运行/编译我的代码时收到此错误 PHP Fatal error: Call to a member function diff() on a non-object in... 但无法弄清楚我做错了什么。

$datetime = date("Y-m-d H:i:s");
$localhost = "localhost";
$conn = mysqli_connect($localhost, $mysqlUsername, $mysqlPassword, $mysqlDB);

if (!$conn)
{
        die("Connection failed: " . mysqli_connect_error());
        echo "Connection to DB failed";
}

$sql = "SELECT * FROM UniqueUsers";
$result = mysqli_query($conn, $sql);

if ($result->num_rows > 0 )
{
        while($row = $result->fetch_assoc())
        {
                $datetime1 = new DateTime($row['worldtime']);
                $interval = $datetime->diff($datetime1);
                echo $interval->format('%R%a days');
        }
}

Answer 1

您的 $datetime 变量不是对象。功能date() 不返回 DateTime 对象，而是返回格式化字符串。

将第一行替换为

$datetime = new DateTime(date("Y-m-d H:i:s"));