<?php
/**
* create_time_range
*
* @param mixed $start start time, e.g., 9:30am or 9:30
* @param mixed $end   end time, e.g., 5:30pm or 17:30
* @param string $by   1 hour, 1 mins, 1 secs, etc.
* @access public
* @return void
*/
function create_time_range($start, $end, $by='30 mins') {

	$start_time = strtotime($start);
	$end_time   = strtotime($end);

	$current    = time();
	$add_time   = strtotime('+'.$by, $current);
	$diff       = $add_time-$current;

   	$times = array();
   	while ($start_time < $end_time) {
       $times[] = $start_time;
       $start_time += $diff;
    }
  	$times[] = $start_time;
  	return $times;
}

// create array of time ranges
$times = create_time_range('9:30', '17:30', '30 mins');

foreach ($times as $key => $time) {
  $times[$key] = date('H:i', $time);
}

?>