php 數字轉換時間

        $timeStr = date("Ymd.His");
        echo $timeStr.'<br/>';
        
        $hour = substr( $timeStr,  9, 2);    //在第8位（從0開始）後取2位
        $minute = substr( $timeStr,  11, 2);
        $second= substr( $timeStr,  13, 2);
        $year= substr( $timeStr,  0, 4);
        $month= substr( $timeStr,  4, 2);
        $day = substr( $timeStr,  6, 2);
        echo "$year-$month-$day $hour:$minute:$second".'<br/>';
        echo date("$year-$month-$day $hour:$minute:$second") .'<br/>';