<?php 
 
 
   /**
    Note: form provide these parameters:
     $start_date
     $new_interval
     $new_frequency
     $end_date  //if no end_date use start date
     $time_block //each time block is 10 or 15 min, this indicates the number of blocks 1 to 10
 
    
    Note: determine settings manually or use database stored configuration  
     $double_book == "Y"; //event double booking
 $repeat == "no";//if no end_date use start date and repeat is no else repeat is yes
    **/
 /*******Note:
        - array repeatEvent(int $startTime, str $interval, int $frequency, int $endTime)
       returns array of UNIX times
    - $startTime and $endTime must be valid UNIX time integer values
    - $interval must be (case-insensitive): 'day', 'week', 'month', or 'year'
    - $frequency must be positive integer (1 = every, 2, = every other, 3 = every 3rd, 4 = every 4th. 5 = every 5th, 6 = every 6th)
 *********/
 function repeatEvent($startTime, $interval, $frequency, $endTime)
    {
     //make sure all paramters are valid
     $startTime = (int) $startTime;
     $endTime = (int) $endTime;
  if($startTime == 0)
      {
               user_error("repeatEvent(): invalid start time");
          return(FALSE);
       }
     
     if($endTime < $startTime)
       {
           user_error("repeatEvent(): invalid end time");
        }
            
     $interval = strtolower(trim($interval));
     if(!in_array($interval, array('day','week','month','year')))
       {
                 user_error("repeatEvent(): Invalid interval '$interval'");
                  return(FALSE);
           }
     $frequency = (int)$frequency;
    if($frequency < 1)
       {
                   user_error("repeatEvent(): Invalid frequency '$frequency'");
                   return(FALSE);
       }
     $schedule = array();
     for($time = $startTime; $time <= $endTime; $time = strtotime("+$frequency $interval", $time))
        {
              $schedule[] = $time;
        }
     return($schedule);
   }

     /**-----------------------insert appointment-----------------------**/
     $sched = repeatEvent(strtotime($start_date), $new_interval, $new_frequency, strtotime($end_date));
   
     //outer loop repeated inserts
     foreach($sched as $date)
         {
      
       //inner loop the number of time blocks
       for($i = 0, $eTime = strtotime($event_time); $i < $time_block; 
           $i++, $eTime = strtotime("+$event_length minutes", $eTime)) 
    { 
      $new_event_time = date('H:i', $eTime); //increment time for new single or multi block event 
   $new_event_date = date('Y-m-d', $date);//increment date for single or repeat event
     
   /**-----------------------check conflicts------------------------**/
      //determine the number of appointments for date and time to determine conflicts
   $event_count = "SELECT count(event_id) 
     FROM cal_appointment
     WHERE event_date = '$new_event_date'
     AND event_time = '$new_event_time '";
     $count = mysqli_query ($mysqli, $event_count);
     while($row = mysqli_fetch_array($count))
      {
       list($book_count) = $row;
      }       
    
    /**----------- tables for inserting information-----------**/
    /**Note: I have removed table fields to simplify example **/
    
    //insert if conflict insert in to cal_repeat_conflict
    $conflict_query = "INSERT INTO cal_repeat_conflict()
          VALUES()";
       
   //no conflicts insert into cal_appointment table 
   $cal_query = "INSERT INTO cal_appointment()
         VALUES();
    
   /**------------------------evaluate event time conflict---------------------**/
   //check to ensure that only allowed number of bookings for time slot is  entered
   if($double_book == "N" && $book_count == 1 && $repeat == "no")
          {
        event_conflict_message();//event time conflict assigned
           }
              elseif($double_book == "Y" && $book_count == 2 && $repeat == "no")
           {
          event_conflict_message();//event time conflict assigned
    }
    elseif($double_book == "N" && $book_count == 1 && $repeat == "yes")
          {
        //insert into table event if time conflict
     mysqli_query($mysqli, $conflict_query)or die(mysqli_error($mysqli));
          }
              elseif($double_book == "Y" && $book_count == 2 && $repeat == "yes")
            {
         //insert into table event if time conflict
        mysqli_query($mysqli, $conflict_query)or die(mysqli_error($mysqli));
     }       
     else
         {
            //no conflicts insert into cal_appointment table 
            mysqli_query($mysqli, $cal_query)or die(mysqli_error($mysqli));
               }
        }//end for loop
         }//end foreach loop
?>