//strtotime 时间转为时间戳
/**
 * @param $actionTime  
 * @param $endTime
 */
function demo($actionTime,$endTime){
    if (strtotime($endTime) < strtotime($actionTime)){
        echo '活动超时啦 宝~';
    }
    $diff = strtotime($endTime) - strtotime($actionTime);
    $day = floor($diff/(3600*24));
    $diff = $diff%(3600*24);                    //除去整天之后剩余的时间
    $hour = floor($diff/3600);
    $diff = $diff%3600;                         //除去整小时之后剩余的时间
    $minute = floor($diff/60);
    $second = $diff%60;                         //除去整分钟之后剩余的时间

    echo '还剩' . $day.'天'.$hour.'小时'.$minute .'分钟'  . $second . '秒';
}

echo demo('2021-09-07 22:00','2022-09-07 22:00');