How to calculate no of working days in php?

function getWorkingDays($startDate, $endDate){
   $begin=strtotime($startDate);
   $end=strtotime($endDate);
   if($begin>$end){
     echo "tartdate is in the future! 
";
      return 0;
   }else{
      $no_days=0;
      $weekends=0;
      while($begin<=$end){
         $no_days++; // no of days in the given interval
         $what_day=date("N",$begin);
         if($what_day>6) { // 6 and 7 are weekend days
            $weekends++;
         };
         $begin+=86400; // +1 day
      };
      $working_days=$no_days-$weekends;
      return $working_days;
   }
}