usort 函数

function getNameFromNumber($num){
   // Used to figure out what the Excel column name would be for a given 0-indexed array of data
   $numeric = ($num-1)%26;
   $letter = chr(65+$numeric);
   $num2 = intval(($num-1) / 26);
   if ( $num2 > 0 ) {
      return getNameFromNumber($num2) . $letter;
   } else {
      return $letter;
   }
}

function GetDevicesbyOwner(){
   global $dbh;

   $this->MakeSafe();

      $sql="SELECT *, (SELECT b.DataCenterID FROM fac_Device a, fac_Cabinet b
      WHERE a.Cabinet=b.CabinetID AND a.DeviceID=search.DeviceID ORDER BY 
      b.DataCenterID, a.Label) DataCenterID FROM fac_Device search WHERE 
      Status<>'Disposed' AND Owner=$this->Owner ORDER BY Label;";

   $deviceList=array();
   foreach($dbh->query($sql) as $deviceRow){
      $deviceList[$deviceRow["DeviceID"]]=Device::RowToObject($deviceRow);
   }

   return $deviceList;
}

function ticksToTime($ticks) {
   $seconds=floor($ticks/100);
   // $date = new DateTime('2000-01-01');
    $dtF=new DateTime("@0");
   $dtT=new DateTime("@$seconds");
   $a=$dtF->diff($dtT)->format('%a');  //%a返回总天数
   $h=$dtF->diff($dtT)->format('%h');  //%h 小时 0--23
   $i=$dtF->diff($dtT)->format('%i');  //%i 分钟 0-59
   $s=$dtF->diff($dtT)->format('%s');  // %s 秒  0-59
   if($a>0){
      return $dtF->diff($dtT)->format('%a days, %h hours, %i minutes and %s seconds');
   }else if($h>0){
      return $dtF->diff($dtT)->format('%h hours, %i minutes and %s seconds');
   }else if($i>0){
      return $dtF->diff($dtT)->format(' %i minutes and %s seconds');
   }else{
      return $dtF->diff($dtT)->format('%s seconds');
   }
}