PHP實現字節數Byte轉換為KB、MB、GB、TB

function getFilesize($num) {
        $p = 0;
        $format = 'bytes';
        if( $num > 0 && $num < 1024 ) {
          $p = 0;
          return number_format($num) . ' ' . $format;
        }
        if( $num >= 1024 && $num < pow(1024, 2) ){
          $p = 1;
          $format = 'KB';
       }
       if ( $num >= pow(1024, 2) && $num < pow(1024, 3) ) {
         $p = 2;
         $format = 'MB';
       }
       if ( $num >= pow(1024, 3) && $num < pow(1024, 4) ) {
         $p = 3;
         $format = 'GB';
       }
       if ( $num >= pow(1024, 4) && $num < pow(1024, 5) ) {
         $p = 3;
         $format = 'TB';
       }
       $num /= pow(1024, $p);
       return number_format($num, 3) . ' ' . $format;
}