public static function bytesToSize($bytes)

 {

         if ($bytes < 1024) {

             return '< 1k';

         } else if ($bytes < 1048576) { // 1024 * 1024

             return round($bytes/1024, 2) .'K';

         } else if ($bytes < 1073741824) { // 1024 * 1024 * 1024

             return round($bytes/1048576, 2) .'M';

         } else {

             return round($bytes/1073741824, 2) .'G';

         }

12 }

 public static function secToStr($sec)

 {

         $hours = floor($sec / 3600);

         $minutes = floor(($sec / 60) % 60);

         $seconds = $sec % 60;

         if ($hours > 0) {

             return sprintf("%02d:%02d:%02d", $hours, $minutes, $seconds);

         } else {

             return sprintf("%d:%02d", $minutes, $seconds);

         }

 }