How can I make an array of times with half hour intervals?

I decided this one was better :)

function hoursRange($lower = 0, $upper = 23, $step = 1, $format = NULL) {

    if ($format === NULL) {
        $format = 'g:ia'; // 9:30pm
    }
    $times = array();
    foreach(range($lower, $upper, $step) as $increment) {
        $increment = number_format($increment, 2);
        list($hour, $minutes) = explode('.', $increment);
        $date = new DateTime($hour . ':' . $minutes * .6);
        $times[(string) $increment] = $date->format($format);
    }
    return $times;
}

Here is my suggestion :

    $start = new \DateTime('00:00');
    $times = 24 * 2; // 24 hours * 30 mins in an hour

    for ($i = 0; $i < $times-1; $i++) {
        $result[] = $start->add(new \DateInterval('PT30M'))->format('H:i A');
    }

    print_r($result);

Hope this help.

Here's an improved version of Alex's function that uses seconds for more precision:

function hoursRange( $lower = 0, $upper = 86400, $step = 3600, $format = '' ) {
    $times = array();

    if ( empty( $format ) ) {
        $format = 'g:i a';
    }

    foreach ( range( $lower, $upper, $step ) as $increment ) {
        $increment = gmdate( 'H:i', $increment );

        list( $hour, $minutes ) = explode( ':', $increment );

        $date = new DateTime( $hour . ':' . $minutes );

        $times[(string) $increment] = $date->format( $format );
    }

    return $times;
}

So, to make an array of times with 1-hour intervals over a 24-hour time period, use the defaults:

hoursRange();

Which will give you the following:

Array
(
    [00:00] => 12:00 am
    [01:00] => 1:00 am
    [02:00] => 2:00 am
    [03:00] => 3:00 am
    [04:00] => 4:00 am
    [05:00] => 5:00 am
    [06:00] => 6:00 am
    [07:00] => 7:00 am
    [08:00] => 8:00 am
    [09:00] => 9:00 am
    [10:00] => 10:00 am
    [11:00] => 11:00 am
    [12:00] => 12:00 pm
    [13:00] => 1:00 pm
    [14:00] => 2:00 pm
    [15:00] => 3:00 pm
    [16:00] => 4:00 pm
    [17:00] => 5:00 pm
    [18:00] => 6:00 pm
    [19:00] => 7:00 pm
    [20:00] => 8:00 pm
    [21:00] => 9:00 pm
    [22:00] => 10:00 pm
    [23:00] => 11:00 pm
)

Here are a few example uses:

// Every 15 Minutes, All Day Long
$range = hoursRange( 0, 86400, 60 * 15 );

// Every 30 Minutes from 8 AM - 5 PM, using Custom Time Format
$range = hoursRange( 28800, 61200, 60 * 30, 'h:i a' );

You can view a working snippet at CodePad.

Thank-you for reopening the question alex.

This is a solution that should resonate with functional programmers.

function halfHourTimes() {
  $formatter = function ($time) {
    if ($time % 3600 == 0) {
      return date('ga', $time);
    } else {
      return date('g:ia', $time);
    }
  };
  $halfHourSteps = range(0, 47*1800, 1800);
  return array_map($formatter, $halfHourSteps);
}