- date: documentation ( source)
- strtotime: documentation ( source)
- printf: documentation ( source)
<?php
$start=strtotime('10:00');
$end=strtotime('21:30');
for ($halfhour=$start;$halfhour<=$end;$halfhour=$halfhour+30*60) {
printf('<option value="%s">%s</option>',date('H:i',$halfhour),date('g:i a',$halfhour));
}
?>