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Generating a drop down list of timezones with PHP

Answer 1

A:

the first option would allow you to take the value from $_POST['whateveryoucalltheselect'] and add it to UTC. or even store that value and then always call UTC + userTZsetting whenever you need it later. seems easiest to me. the last option would be much more valuable if timezones changed frequently.

Brandon H 2009-11-13 04:15:08

Answer 2

A:

None of them. Instead prepare an array in PHP with those timezones. Like

$arr[0] = "(GMT+02:00) Harare, Pretoria";
$arr[1] = "(GMT+03:00) Jerusalem";

or

$arr[0] = array("America/Campo_Grande", "(GMT+02:00) Harare, Pretoria");
$arr[1] = array("America/Israel", "(GMT+03:00) Jerusalem");

and so on. Then generate form based on this array:

foreach ($arr as $k => $v)
   $str .= "<option value=$k>$v[1]</option>";

And then you may easily switch with different formats with just code modification in above line. Also validation will be much easier and don't require regular expressions. Just compare value sent by POST or GET with an array. Now it's easy to set $arr[$value_sent_by_form][0] holds PHP compatible value while $arr[$value_sent_by_form][1] user friendly value.

doc 2009-11-13 04:26:05

How would you know what UTC timezone to set if the only values you have are a numeric key and a human friendly string? I think you mean to set the array keys to the actual values like in list one. Also, whatever I choose you can be certain that it will find it's way into a PHP array. ;)

Xeoncross 2009-11-13 04:28:59

Then prepare array like this:$arr[0] = array("America/Campo_Grande","(GMT+02:00) Harare, Pretoria");

doc 2009-11-13 04:30:46

Answer 3

+5 A:

I would do it in PHP, except I would avoid doing preg_match 100 some times and do this to generate your list.

static $regions = array(
    'Africa' => DateTimeZone::AFRICA,
    'America' => DateTimeZone::AMERICA,
    'Antarctica' => DateTimeZone::ANTARCTICA,
    'Aisa' => DateTimeZone::ASIA,
    'Atlantic' => DateTimeZone::ATLANTIC,
    'Europe' => DateTimeZone::EUROPE,
    'Indian' => DateTimeZone::INDIAN,
    'Pacific' => DateTimeZone::PACIFIC
);
foreach ($regions as $name => $mask) {
    $tzlist[] = DateTimeZone::listIdentifiers($mask);
}

And I would use PHP's names for the 'timezones' and forget about GMT offsets, which will change based on DST. Code like that in phpbb is only that way b/c they are still supporting PHP4 and can't rely on the DateTime or DateTimeZone objects being there.

2009-11-13 04:37:35

Using PHP 5.2.5 I'm getting `Undefined class constant 'AFRICA'` when I try to use the DateTimeZone class. I checked the defined classes and it's listed so maybe windows needs something else for this to work.

Xeoncross 2009-11-14 21:59:34

Answer 4

+2 A:

I would do it with the following code which is similar to the accepted answer (I'm aware the code could be refactored :) ):

    $list = DateTimeZone::listAbbreviations();
    $idents = DateTimeZone::listIdentifiers();

    $data = $offset = $added = array();
    foreach ($list as $abbr => $info) {
        foreach ($info as $zone) {
            if ( ! empty($zone['timezone_id'])
                AND
                ! in_array($zone['timezone_id'], $added)
                AND 
                  in_array($zone['timezone_id'], $idents)) {
                $z = new DateTimeZone($zone['timezone_id']);
                $c = new DateTime(null, $z);
                $zone['time'] = $c->format('H:i a');
                $data[] = $zone;
                $offset[] = $z->getOffset($c);
                $added[] = $zone['timezone_id'];
            }
        }
    }

    array_multisort($offset, SORT_ASC, $data);
    $options = array();
    foreach ($data as $key => $row) {
        $options[$row['timezone_id']] = $row['time'] . ' - '
                                        . formatOffset($row['offset']) 
                                        . ' ' . $row['timezone_id'];
    }

    // now you can use $options;

function formatOffset($offset) {
        $hours = $offset / 3600;
        $remainder = $offset % 3600;
        $sign = $hours > 0 ? '+' : '-';
        $hour = (int) abs($hours);
        $minutes = (int) abs($remainder / 60);

        if ($hour == 0 AND $minutes == 0) {
            $sign = ' ';
        }
        return 'GMT' . $sign . str_pad($hour, 2, '0', STR_PAD_LEFT) 
                .':'. str_pad($minutes,2, '0');

}

It produces something like:

<option value="America/Boise" label="02:10 am - GMT-06:00 America/Boise">02:10 am - GMT-06:00 America/Boise</option>

<option value="America/Denver" label="02:10 am - GMT-06:00 America/Denver">02:10 am - GMT-06:00 America/Denver</option>
<option value="America/Edmonton" label="02:10 am - GMT-06:00 America/Edmonton">02:10 am - GMT-06:00 America/Edmonton</option>
<option value="America/Inuvik" label="02:10 am - GMT-06:00 America/Inuvik">02:10 am - GMT-06:00 America/Inuvik</option>
<option value="America/Shiprock" label="02:10 am - GMT-06:00 America/Shiprock">02:10 am - GMT-06:00 America/Shiprock</option>

<option value="America/Belize" label="02:10 am - GMT-05:00 America/Belize">02:10 am - GMT-05:00 America/Belize</option>

Hope that helps a bit and/or inspire you to come with something better.

Favio 2010-05-15 08:12:28

Thanks, the more options the better. Listing the actual time also helps people who don't know what timezone they are in.

Xeoncross 2010-05-16 17:48:19

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Generating a drop down list of timezones with PHP

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