Gerando uma lista suspensa de fusos horários com PHP

A maioria dos sites precisa de alguma maneira de mostrar as datas no site no fuso horário preferido dos usuários. Abaixo estão duas listas que eu encontrei e, em seguida, um método usando a classe DateTime embutida no PHP 5.

Preciso de ajuda para saber qual desses seria o melhor tentar usar ao tentar obter o deslocamento UTC do usuário no registro.

1:

<option value="-12">[UTC - 12] Baker Island Time</option>
<option value="-11">[UTC - 11] Niue Time, Samoa Standard Time</option>
<option value="-10">[UTC - 10] Hawaii-Aleutian Standard Time, Cook Island Time</option>
<option value="-9.5">[UTC - 9:30] Marquesas Islands Time</option>
<option value="-9">[UTC - 9] Alaska Standard Time, Gambier Island Time</option>
<option value="-8">[UTC - 8] Pacific Standard Time</option>
<option value="-7">[UTC - 7] Mountain Standard Time</option>
<option value="-6">[UTC - 6] Central Standard Time</option>
<option value="-5">[UTC - 5] Eastern Standard Time</option>
<option value="-4.5">[UTC - 4:30] Venezuelan Standard Time</option>
<option value="-4">[UTC - 4] Atlantic Standard Time</option>
<option value="-3.5">[UTC - 3:30] Newfoundland Standard Time</option>
<option value="-3">[UTC - 3] Amazon Standard Time, Central Greenland Time</option>
<option value="-2">[UTC - 2] Fernando de Noronha Time, South Georgia &amp; the South Sandwich Islands Time</option>
<option value="-1">[UTC - 1] Azores Standard Time, Cape Verde Time, Eastern Greenland Time</option>
<option value="0" selected="selected">[UTC] Western European Time, Greenwich Mean Time</option>
<option value="1">[UTC + 1] Central European Time, West African Time</option>
<option value="2">[UTC + 2] Eastern European Time, Central African Time</option>
<option value="3">[UTC + 3] Moscow Standard Time, Eastern African Time</option>
<option value="3.5">[UTC + 3:30] Iran Standard Time</option>
<option value="4">[UTC + 4] Gulf Standard Time, Samara Standard Time</option>
<option value="4.5">[UTC + 4:30] Afghanistan Time</option>
<option value="5">[UTC + 5] Pakistan Standard Time, Yekaterinburg Standard Time</option>
<option value="5.5">[UTC + 5:30] Indian Standard Time, Sri Lanka Time</option>
<option value="5.75">[UTC + 5:45] Nepal Time</option>
<option value="6">[UTC + 6] Bangladesh Time, Bhutan Time, Novosibirsk Standard Time</option>
<option value="6.5">[UTC + 6:30] Cocos Islands Time, Myanmar Time</option>
<option value="7">[UTC + 7] Indochina Time, Krasnoyarsk Standard Time</option>
<option value="8">[UTC + 8] Chinese Standard Time, Australian Western Standard Time, Irkutsk Standard Time</option>
<option value="8.75">[UTC + 8:45] Southeastern Western Australia Standard Time</option>
<option value="9">[UTC + 9] Japan Standard Time, Korea Standard Time, Chita Standard Time</option>
<option value="9.5">[UTC + 9:30] Australian Central Standard Time</option>
<option value="10">[UTC + 10] Australian Eastern Standard Time, Vladivostok Standard Time</option>
<option value="10.5">[UTC + 10:30] Lord Howe Standard Time</option>
<option value="11">[UTC + 11] Solomon Island Time, Magadan Standard Time</option>
<option value="11.5">[UTC + 11:30] Norfolk Island Time</option>
<option value="12">[UTC + 12] New Zealand Time, Fiji Time, Kamchatka Standard Time</option>
<option value="12.75">[UTC + 12:45] Chatham Islands Time</option>
<option value="13">[UTC + 13] Tonga Time, Phoenix Islands Time</option>
<option value="14">[UTC + 14] Line Island Time</option>

Ou usando valores compatíveis com PHP:

<option value="Pacific/Midway">(GMT-11:00) Midway Island, Samoa</option>
<option value="America/Adak">(GMT-10:00) Hawaii-Aleutian</option>
<option value="Etc/GMT+10">(GMT-10:00) Hawaii</option>
<option value="Pacific/Marquesas">(GMT-09:30) Marquesas Islands</option>
<option value="Pacific/Gambier">(GMT-09:00) Gambier Islands</option>
<option value="America/Anchorage">(GMT-09:00) Alaska</option>
<option value="America/Ensenada">(GMT-08:00) Tijuana, Baja California</option>
<option value="Etc/GMT+8">(GMT-08:00) Pitcairn Islands</option>
<option value="America/Los_Angeles">(GMT-08:00) Pacific Time (US & Canada)</option>
<option value="America/Denver">(GMT-07:00) Mountain Time (US & Canada)</option>
<option value="America/Chihuahua">(GMT-07:00) Chihuahua, La Paz, Mazatlan</option>
<option value="America/Dawson_Creek">(GMT-07:00) Arizona</option>
<option value="America/Belize">(GMT-06:00) Saskatchewan, Central America</option>
<option value="America/Cancun">(GMT-06:00) Guadalajara, Mexico City, Monterrey</option>
<option value="Chile/EasterIsland">(GMT-06:00) Easter Island</option>
<option value="America/Chicago">(GMT-06:00) Central Time (US & Canada)</option>
<option value="America/New_York">(GMT-05:00) Eastern Time (US & Canada)</option>
<option value="America/Havana">(GMT-05:00) Cuba</option>
<option value="America/Bogota">(GMT-05:00) Bogota, Lima, Quito, Rio Branco</option>
<option value="America/Caracas">(GMT-04:30) Caracas</option>
<option value="America/Santiago">(GMT-04:00) Santiago</option>
<option value="America/La_Paz">(GMT-04:00) La Paz</option>
<option value="Atlantic/Stanley">(GMT-04:00) Faukland Islands</option>
<option value="America/Campo_Grande">(GMT-04:00) Brazil</option>
<option value="America/Goose_Bay">(GMT-04:00) Atlantic Time (Goose Bay)</option>
<option value="America/Glace_Bay">(GMT-04:00) Atlantic Time (Canada)</option>
<option value="America/St_Johns">(GMT-03:30) Newfoundland</option>
<option value="America/Araguaina">(GMT-03:00) UTC-3</option>
<option value="America/Montevideo">(GMT-03:00) Montevideo</option>
<option value="America/Miquelon">(GMT-03:00) Miquelon, St. Pierre</option>
<option value="America/Godthab">(GMT-03:00) Greenland</option>
<option value="America/Argentina/Buenos_Aires">(GMT-03:00) Buenos Aires</option>
<option value="America/Sao_Paulo">(GMT-03:00) Brasilia</option>
<option value="America/Noronha">(GMT-02:00) Mid-Atlantic</option>
<option value="Atlantic/Cape_Verde">(GMT-01:00) Cape Verde Is.</option>
<option value="Atlantic/Azores">(GMT-01:00) Azores</option>
<option value="Europe/Belfast">(GMT) Greenwich Mean Time : Belfast</option>
<option value="Europe/Dublin">(GMT) Greenwich Mean Time : Dublin</option>
<option value="Europe/Lisbon">(GMT) Greenwich Mean Time : Lisbon</option>
<option value="Europe/London">(GMT) Greenwich Mean Time : London</option>
<option value="Africa/Abidjan">(GMT) Monrovia, Reykjavik</option>
<option value="Europe/Amsterdam">(GMT+01:00) Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna</option>
<option value="Europe/Belgrade">(GMT+01:00) Belgrade, Bratislava, Budapest, Ljubljana, Prague</option>
<option value="Europe/Brussels">(GMT+01:00) Brussels, Copenhagen, Madrid, Paris</option>
<option value="Africa/Algiers">(GMT+01:00) West Central Africa</option>
<option value="Africa/Windhoek">(GMT+01:00) Windhoek</option>
<option value="Asia/Beirut">(GMT+02:00) Beirut</option>
<option value="Africa/Cairo">(GMT+02:00) Cairo</option>
<option value="Asia/Gaza">(GMT+02:00) Gaza</option>
<option value="Africa/Blantyre">(GMT+02:00) Harare, Pretoria</option>
<option value="Asia/Jerusalem">(GMT+02:00) Jerusalem</option>
<option value="Europe/Minsk">(GMT+02:00) Minsk</option>
<option value="Asia/Damascus">(GMT+02:00) Syria</option>
<option value="Europe/Moscow">(GMT+03:00) Moscow, St. Petersburg, Volgograd</option>
<option value="Africa/Addis_Ababa">(GMT+03:00) Nairobi</option>
<option value="Asia/Tehran">(GMT+03:30) Tehran</option>
<option value="Asia/Dubai">(GMT+04:00) Abu Dhabi, Muscat</option>
<option value="Asia/Yerevan">(GMT+04:00) Yerevan</option>
<option value="Asia/Kabul">(GMT+04:30) Kabul</option>
<option value="Asia/Yekaterinburg">(GMT+05:00) Ekaterinburg</option>
<option value="Asia/Tashkent">(GMT+05:00) Tashkent</option>
<option value="Asia/Kolkata">(GMT+05:30) Chennai, Kolkata, Mumbai, New Delhi</option>
<option value="Asia/Katmandu">(GMT+05:45) Kathmandu</option>
<option value="Asia/Dhaka">(GMT+06:00) Astana, Dhaka</option>
<option value="Asia/Novosibirsk">(GMT+06:00) Novosibirsk</option>
<option value="Asia/Rangoon">(GMT+06:30) Yangon (Rangoon)</option>
<option value="Asia/Bangkok">(GMT+07:00) Bangkok, Hanoi, Jakarta</option>
<option value="Asia/Krasnoyarsk">(GMT+07:00) Krasnoyarsk</option>
<option value="Asia/Hong_Kong">(GMT+08:00) Beijing, Chongqing, Hong Kong, Urumqi</option>
<option value="Asia/Irkutsk">(GMT+08:00) Irkutsk, Ulaan Bataar</option>
<option value="Australia/Perth">(GMT+08:00) Perth</option>
<option value="Australia/Eucla">(GMT+08:45) Eucla</option>
<option value="Asia/Tokyo">(GMT+09:00) Osaka, Sapporo, Tokyo</option>
<option value="Asia/Seoul">(GMT+09:00) Seoul</option>
<option value="Asia/Yakutsk">(GMT+09:00) Yakutsk</option>
<option value="Australia/Adelaide">(GMT+09:30) Adelaide</option>
<option value="Australia/Darwin">(GMT+09:30) Darwin</option>
<option value="Australia/Brisbane">(GMT+10:00) Brisbane</option>
<option value="Australia/Hobart">(GMT+10:00) Hobart</option>
<option value="Asia/Vladivostok">(GMT+10:00) Vladivostok</option>
<option value="Australia/Lord_Howe">(GMT+10:30) Lord Howe Island</option>
<option value="Etc/GMT-11">(GMT+11:00) Solomon Is., New Caledonia</option>
<option value="Asia/Magadan">(GMT+11:00) Magadan</option>
<option value="Pacific/Norfolk">(GMT+11:30) Norfolk Island</option>
<option value="Asia/Anadyr">(GMT+12:00) Anadyr, Kamchatka</option>
<option value="Pacific/Auckland">(GMT+12:00) Auckland, Wellington</option>
<option value="Etc/GMT-12">(GMT+12:00) Fiji, Kamchatka, Marshall Is.</option>
<option value="Pacific/Chatham">(GMT+12:45) Chatham Islands</option>
<option value="Pacific/Tongatapu">(GMT+13:00) Nuku'alofa</option>
<option value="Pacific/Kiritimati">(GMT+14:00) Kiritimati</option>

Ou apenas usando o próprio PHP:

$timezones = DateTimeZone::listAbbreviations();

$cities = array();
foreach( $timezones as $key => $zones )
{
    foreach( $zones as $id => $zone )
    {
        /**
         * Only get timezones explicitely not part of "Others".
         * @see http://www.php.net/manual/en/timezones.others.php
         */
        if ( preg_match( '/^(America|Antartica|Arctic|Asia|Atlantic|Europe|Indian|Pacific)\//', $zone['timezone_id'] ) 
            && $zone['timezone_id']) {
            $cities[$zone['timezone_id']][] = $key;
        }
    }
}

// For each city, have a comma separated list of all possible timezones for that city.
foreach( $cities as $key => $value )
    $cities[$key] = join( ', ', $value);

// Only keep one city (the first and also most important) for each set of possibilities. 
$cities = array_unique( $cities );

// Sort by area/city name.
ksort( $cities );

Parece que o último seria o mais seguro, pois aumentaria com o lançamento do PHP. Você também pode inverter essa matriz quando necessário para vincular fusos horários a nomes de cidades.

Eu faria isso em PHP, exceto que evitaria fazer o preg_match 100 algumas vezes e faria isso para gerar sua lista.

$tzlist = DateTimeZone::listIdentifiers(DateTimeZone::ALL);

Além disso, eu usaria os nomes do PHP para os 'fusos horários' e esqueceria as compensações GMT, que serão alteradas com base no horário de verão. Um código assim no phpbb é apenas dessa forma porque eles ainda suportam o PHP4 e não podem confiar nos objetos DateTime ou DateTimeZone que estão lá.

Seguindo o exemplo de user210179 acima, escrevi a seguinte função para gerar uma lista de todos os fusos horários com seus desvios:

function generate_timezone_list()
{
    static $regions = array(
        DateTimeZone::AFRICA,
        DateTimeZone::AMERICA,
        DateTimeZone::ANTARCTICA,
        DateTimeZone::ASIA,
        DateTimeZone::ATLANTIC,
        DateTimeZone::AUSTRALIA,
        DateTimeZone::EUROPE,
        DateTimeZone::INDIAN,
        DateTimeZone::PACIFIC,
    );

    $timezones = array();
    foreach( $regions as $region )
    {
        $timezones = array_merge( $timezones, DateTimeZone::listIdentifiers( $region ) );
    }

    $timezone_offsets = array();
    foreach( $timezones as $timezone )
    {
        $tz = new DateTimeZone($timezone);
        $timezone_offsets[$timezone] = $tz->getOffset(new DateTime);
    }

    // sort timezone by offset
    asort($timezone_offsets);

    $timezone_list = array();
    foreach( $timezone_offsets as $timezone => $offset )
    {
        $offset_prefix = $offset < 0 ? '-' : '+';
        $offset_formatted = gmdate( 'H:i', abs($offset) );

        $pretty_offset = "UTC${offset_prefix}${offset_formatted}";

        $timezone_list[$timezone] = "(${pretty_offset}) $timezone";
    }

    return $timezone_list;
}

Isso irá gerar uma matriz parecida com:

[Pacific/Midway] => (UTC-11:00) Pacific/Midway
[Pacific/Pago_Pago] => (UTC-11:00) Pacific/Pago_Pago
[Pacific/Niue] => (UTC-11:00) Pacific/Niue
[Pacific/Honolulu] => (UTC-10:00) Pacific/Honolulu
[Pacific/Fakaofo] => (UTC-10:00) Pacific/Fakaofo
…

Atualmente, ele é classificado por deslocamentos, mas você pode classificar facilmente pelo nome do fuso horário executando um em ksort()vez de asort().

Apesar do número de respostas existentes, eu fiz outra solução para esse problema. Os profissionais da minha implementação são:

• A lista de fusos horários é gerada dinamicamente e, portanto, é atualizada automaticamente quando os fusos horários podem mudar (em PHP).
• Os nomes de fuso horário são prettificados. Por exemplo, "America / St_Barthelemy" se torna "America, St. Barthelemy".
• Os fusos horários são classificados em deslocamento e nome. A resposta de Toland classifica apenas no deslocamento, resultando em grupos de fusos horários não classificados no mesmo deslocamento.
• As informações de deslocamento não são recuperadas DateTimeZone::listAbbreviations, pois esse método também retorna informações históricas do fuso horário . A resposta de Favio usa esse método, que resulta em compensações incorretas (históricas)
• A lista de fusos horários é gerada apenas quando solicitada pela primeira vez (e 'armazenada em cache' usando uma variável estática).

Aqui está o código completo:

function timezone_list() {
    static $timezones = null;

    if ($timezones === null) {
        $timezones = [];
        $offsets = [];
        $now = new DateTime('now', new DateTimeZone('UTC'));

        foreach (DateTimeZone::listIdentifiers() as $timezone) {
            $now->setTimezone(new DateTimeZone($timezone));
            $offsets[] = $offset = $now->getOffset();
            $timezones[$timezone] = '(' . format_GMT_offset($offset) . ') ' . format_timezone_name($timezone);
        }

        array_multisort($offsets, $timezones);
    }

    return $timezones;
}

function format_GMT_offset($offset) {
    $hours = intval($offset / 3600);
    $minutes = abs(intval($offset % 3600 / 60));
    return 'GMT' . ($offset ? sprintf('%+03d:%02d', $hours, $minutes) : '');
}

function format_timezone_name($name) {
    $name = str_replace('/', ', ', $name);
    $name = str_replace('_', ' ', $name);
    $name = str_replace('St ', 'St. ', $name);
    return $name;
}

E aqui está um exemplo da saída

Array
(
    [Pacific/Midway]    => (GMT-11:00) Pacific, Midway
    [Pacific/Niue]      => (GMT-11:00) Pacific, Niue
    [Pacific/Pago_Pago] => (GMT-11:00) Pacific, Pago Pago
    [America/Adak]      => (GMT-10:00) America, Adak
    [Pacific/Honolulu]  => (GMT-10:00) Pacific, Honolulu
    [Pacific/Johnston]  => (GMT-10:00) Pacific, Johnston
    [Pacific/Rarotonga] => (GMT-10:00) Pacific, Rarotonga
    [Pacific/Tahiti]    => (GMT-10:00) Pacific, Tahiti
    [Pacific/Marquesas] => (GMT-09:30) Pacific, Marquesas
    [America/Anchorage] => (GMT-09:00) America, Anchorage
    ...
)

Eu faria isso com o código a seguir, que é semelhante à resposta aceita (sei que o código pode ser refatorado :)):

    $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');
                $offset[] = $zone['offset'] = $z->getOffset($c);
                $data[] = $zone;
                $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');

}

Produz algo como:

<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>

Espero que ajude um pouco e / ou inspire você a vir com algo melhor.

Você pode criar uma lista suspensa muito fácil a partir dessa matriz (era uma tarefa demorada reunir isso e testá-lo). Já usamos essa lista em alguns de nossos aplicativos.

É muito importante armazenar identificadores de fuso horário no seu banco de dados e não apenas o deslocamento do fuso horário como "GMT + 2", devido ao horário de verão.

ATUALIZAR

Atualizei / corrigi a lista de fusos horários (também faça o checkout: https://github.com/paptamas/timezones ):

<?php
$timezones = array (
'(GMT-11:00) Midway Island' => 'Pacific/Midway',
'(GMT-11:00) Samoa' => 'Pacific/Samoa',
'(GMT-10:00) Hawaii' => 'Pacific/Honolulu',
'(GMT-09:00) Alaska' => 'US/Alaska',
'(GMT-08:00) Pacific Time (US &amp; Canada)' => 'America/Los_Angeles',
'(GMT-08:00) Tijuana' => 'America/Tijuana',
'(GMT-07:00) Arizona' => 'US/Arizona',
'(GMT-07:00) Chihuahua' => 'America/Chihuahua',
'(GMT-07:00) La Paz' => 'America/Chihuahua',
'(GMT-07:00) Mazatlan' => 'America/Mazatlan',
'(GMT-07:00) Mountain Time (US &amp; Canada)' => 'US/Mountain',
'(GMT-06:00) Central America' => 'America/Managua',
'(GMT-06:00) Central Time (US &amp; Canada)' => 'US/Central',
'(GMT-06:00) Guadalajara' => 'America/Mexico_City',
'(GMT-06:00) Mexico City' => 'America/Mexico_City',
'(GMT-06:00) Monterrey' => 'America/Monterrey',
'(GMT-06:00) Saskatchewan' => 'Canada/Saskatchewan',
'(GMT-05:00) Bogota' => 'America/Bogota',
'(GMT-05:00) Eastern Time (US &amp; Canada)' => 'US/Eastern',
'(GMT-05:00) Indiana (East)' => 'US/East-Indiana',
'(GMT-05:00) Lima' => 'America/Lima',
'(GMT-05:00) Quito' => 'America/Bogota',
'(GMT-04:00) Atlantic Time (Canada)' => 'Canada/Atlantic',
'(GMT-04:30) Caracas' => 'America/Caracas',
'(GMT-04:00) La Paz' => 'America/La_Paz',
'(GMT-04:00) Santiago' => 'America/Santiago',
'(GMT-03:30) Newfoundland' => 'Canada/Newfoundland',
'(GMT-03:00) Brasilia' => 'America/Sao_Paulo',
'(GMT-03:00) Buenos Aires' => 'America/Argentina/Buenos_Aires',
'(GMT-03:00) Georgetown' => 'America/Argentina/Buenos_Aires',
'(GMT-03:00) Greenland' => 'America/Godthab',
'(GMT-02:00) Mid-Atlantic' => 'America/Noronha',
'(GMT-01:00) Azores' => 'Atlantic/Azores',
'(GMT-01:00) Cape Verde Is.' => 'Atlantic/Cape_Verde',
'(GMT+00:00) Casablanca' => 'Africa/Casablanca',
'(GMT+00:00) Edinburgh' => 'Europe/London',
'(GMT+00:00) Greenwich Mean Time : Dublin' => 'Etc/Greenwich',
'(GMT+00:00) Lisbon' => 'Europe/Lisbon',
'(GMT+00:00) London' => 'Europe/London',
'(GMT+00:00) Monrovia' => 'Africa/Monrovia',
'(GMT+00:00) UTC' => 'UTC',
'(GMT+01:00) Amsterdam' => 'Europe/Amsterdam',
'(GMT+01:00) Belgrade' => 'Europe/Belgrade',
'(GMT+01:00) Berlin' => 'Europe/Berlin',
'(GMT+01:00) Bern' => 'Europe/Berlin',
'(GMT+01:00) Bratislava' => 'Europe/Bratislava',
'(GMT+01:00) Brussels' => 'Europe/Brussels',
'(GMT+01:00) Budapest' => 'Europe/Budapest',
'(GMT+01:00) Copenhagen' => 'Europe/Copenhagen',
'(GMT+01:00) Ljubljana' => 'Europe/Ljubljana',
'(GMT+01:00) Madrid' => 'Europe/Madrid',
'(GMT+01:00) Paris' => 'Europe/Paris',
'(GMT+01:00) Prague' => 'Europe/Prague',
'(GMT+01:00) Rome' => 'Europe/Rome',
'(GMT+01:00) Sarajevo' => 'Europe/Sarajevo',
'(GMT+01:00) Skopje' => 'Europe/Skopje',
'(GMT+01:00) Stockholm' => 'Europe/Stockholm',
'(GMT+01:00) Vienna' => 'Europe/Vienna',
'(GMT+01:00) Warsaw' => 'Europe/Warsaw',
'(GMT+01:00) West Central Africa' => 'Africa/Lagos',
'(GMT+01:00) Zagreb' => 'Europe/Zagreb',
'(GMT+02:00) Athens' => 'Europe/Athens',
'(GMT+02:00) Bucharest' => 'Europe/Bucharest',
'(GMT+02:00) Cairo' => 'Africa/Cairo',
'(GMT+02:00) Harare' => 'Africa/Harare',
'(GMT+02:00) Helsinki' => 'Europe/Helsinki',
'(GMT+02:00) Istanbul' => 'Europe/Istanbul',
'(GMT+02:00) Jerusalem' => 'Asia/Jerusalem',
'(GMT+02:00) Kyiv' => 'Europe/Helsinki',
'(GMT+02:00) Pretoria' => 'Africa/Johannesburg',
'(GMT+02:00) Riga' => 'Europe/Riga',
'(GMT+02:00) Sofia' => 'Europe/Sofia',
'(GMT+02:00) Tallinn' => 'Europe/Tallinn',
'(GMT+02:00) Vilnius' => 'Europe/Vilnius',
'(GMT+03:00) Baghdad' => 'Asia/Baghdad',
'(GMT+03:00) Kuwait' => 'Asia/Kuwait',
'(GMT+03:00) Minsk' => 'Europe/Minsk',
'(GMT+03:00) Nairobi' => 'Africa/Nairobi',
'(GMT+03:00) Riyadh' => 'Asia/Riyadh',
'(GMT+03:00) Volgograd' => 'Europe/Volgograd',
'(GMT+03:30) Tehran' => 'Asia/Tehran',
'(GMT+04:00) Abu Dhabi' => 'Asia/Muscat',
'(GMT+04:00) Baku' => 'Asia/Baku',
'(GMT+04:00) Moscow' => 'Europe/Moscow',
'(GMT+04:00) Muscat' => 'Asia/Muscat',
'(GMT+04:00) St. Petersburg' => 'Europe/Moscow',
'(GMT+04:00) Tbilisi' => 'Asia/Tbilisi',
'(GMT+04:00) Yerevan' => 'Asia/Yerevan',
'(GMT+04:30) Kabul' => 'Asia/Kabul',
'(GMT+05:00) Islamabad' => 'Asia/Karachi',
'(GMT+05:00) Karachi' => 'Asia/Karachi',
'(GMT+05:00) Tashkent' => 'Asia/Tashkent',
'(GMT+05:30) Chennai' => 'Asia/Calcutta',
'(GMT+05:30) Kolkata' => 'Asia/Kolkata',
'(GMT+05:30) Mumbai' => 'Asia/Calcutta',
'(GMT+05:30) New Delhi' => 'Asia/Calcutta',
'(GMT+05:30) Sri Jayawardenepura' => 'Asia/Calcutta',
'(GMT+05:45) Kathmandu' => 'Asia/Katmandu',
'(GMT+06:00) Almaty' => 'Asia/Almaty',
'(GMT+06:00) Astana' => 'Asia/Dhaka',
'(GMT+06:00) Dhaka' => 'Asia/Dhaka',
'(GMT+06:00) Ekaterinburg' => 'Asia/Yekaterinburg',
'(GMT+06:30) Rangoon' => 'Asia/Rangoon',
'(GMT+07:00) Bangkok' => 'Asia/Bangkok',
'(GMT+07:00) Hanoi' => 'Asia/Bangkok',
'(GMT+07:00) Jakarta' => 'Asia/Jakarta',
'(GMT+07:00) Novosibirsk' => 'Asia/Novosibirsk',
'(GMT+08:00) Beijing' => 'Asia/Hong_Kong',
'(GMT+08:00) Chongqing' => 'Asia/Chongqing',
'(GMT+08:00) Hong Kong' => 'Asia/Hong_Kong',
'(GMT+08:00) Krasnoyarsk' => 'Asia/Krasnoyarsk',
'(GMT+08:00) Kuala Lumpur' => 'Asia/Kuala_Lumpur',
'(GMT+08:00) Perth' => 'Australia/Perth',
'(GMT+08:00) Singapore' => 'Asia/Singapore',
'(GMT+08:00) Taipei' => 'Asia/Taipei',
'(GMT+08:00) Ulaan Bataar' => 'Asia/Ulan_Bator',
'(GMT+08:00) Urumqi' => 'Asia/Urumqi',
'(GMT+09:00) Irkutsk' => 'Asia/Irkutsk',
'(GMT+09:00) Osaka' => 'Asia/Tokyo',
'(GMT+09:00) Sapporo' => 'Asia/Tokyo',
'(GMT+09:00) Seoul' => 'Asia/Seoul',
'(GMT+09:00) Tokyo' => 'Asia/Tokyo',
'(GMT+09:30) Adelaide' => 'Australia/Adelaide',
'(GMT+09:30) Darwin' => 'Australia/Darwin',
'(GMT+10:00) Brisbane' => 'Australia/Brisbane',
'(GMT+10:00) Canberra' => 'Australia/Canberra',
'(GMT+10:00) Guam' => 'Pacific/Guam',
'(GMT+10:00) Hobart' => 'Australia/Hobart',
'(GMT+10:00) Melbourne' => 'Australia/Melbourne',
'(GMT+10:00) Port Moresby' => 'Pacific/Port_Moresby',
'(GMT+10:00) Sydney' => 'Australia/Sydney',
'(GMT+10:00) Yakutsk' => 'Asia/Yakutsk',
'(GMT+11:00) Vladivostok' => 'Asia/Vladivostok',
'(GMT+12:00) Auckland' => 'Pacific/Auckland',
'(GMT+12:00) Fiji' => 'Pacific/Fiji',
'(GMT+12:00) International Date Line West' => 'Pacific/Kwajalein',
'(GMT+12:00) Kamchatka' => 'Asia/Kamchatka',
'(GMT+12:00) Magadan' => 'Asia/Magadan',
'(GMT+12:00) Marshall Is.' => 'Pacific/Fiji',
'(GMT+12:00) New Caledonia' => 'Asia/Magadan',
'(GMT+12:00) Solomon Is.' => 'Asia/Magadan',
'(GMT+12:00) Wellington' => 'Pacific/Auckland',
'(GMT+13:00) Nuku\'alofa' => 'Pacific/Tongatapu'
);
?>   

Editando a resposta do Tamas para remover todas as "outras" entradas que o site php.net diz que não devem mais ser usadas.

Talvez não importe, mas apenas seguindo as práticas recomendadas. Consulte o aviso na parte inferior de: http://fr2.php.net/manual/en/timezones.others.php

Além disso, embora esta lista tenha os Açores como GMT -1, na verdade acho que é o mesmo (pelo menos às vezes) como GMT, mas não tenho certeza.

Edição para oferecer isso no sql, para que você possa criar a lista suspensa em um formulário e, em vez disso, vincular a resposta do usuário a um índice.

Editando novamente para remover o espaço inicial

CREATE TABLE IF NOT EXISTS `timezones` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(44) DEFAULT NULL,
  `timezone` varchar(30) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=141 ;

--
-- Dumping data for table `timezones`
--

INSERT INTO `timezones` (`id`, `name`, `timezone`) VALUES
(1, '(GMT-11:00) Midway Island ', 'Pacific/Midway'),
(2, '(GMT-11:00) Samoa ', 'Pacific/Samoa'),
(3, '(GMT-10:00) Hawaii ', 'Pacific/Honolulu'),
(4, '(GMT-09:00) Alaska ', 'America/Anchorage'),
(5, '(GMT-08:00) Pacific Time (US & Canada) ', 'America/Los_Angeles'),
(6, '(GMT-08:00) Tijuana ', 'America/Tijuana'),
(7, '(GMT-07:00) Chihuahua ', 'America/Chihuahua'),
(8, '(GMT-07:00) La Paz ', 'America/Chihuahua'),
(9, '(GMT-07:00) Mazatlan ', 'America/Mazatlan'),
(10, '(GMT-07:00) Mountain Time (US & Canada) ', 'America/Denver'),
(11, '(GMT-06:00) Central America ', 'America/Managua'),
(12, '(GMT-06:00) Central Time (US & Canada) ', 'America/Chicago'),
(13, '(GMT-06:00) Guadalajara ', 'America/Mexico_City'),
(14, '(GMT-06:00) Mexico City ', 'America/Mexico_City'),
(15, '(GMT-06:00) Monterrey ', 'America/Monterrey'),
(16, '(GMT-05:00) Bogota ', 'America/Bogota'),
(17, '(GMT-05:00) Eastern Time (US & Canada) ', 'America/New_York'),
(18, '(GMT-05:00) Lima ', 'America/Lima'),
(19, '(GMT-05:00) Quito ', 'America/Bogota'),
(20, '(GMT-04:00) Atlantic Time (Canada) ', 'Canada/Atlantic'),
(21, '(GMT-04:30) Caracas ', 'America/Caracas'),
(22, '(GMT-04:00) La Paz ', 'America/La_Paz'),
(23, '(GMT-04:00) Santiago ', 'America/Santiago'),
(24, '(GMT-03:30) Newfoundland ', 'America/St_Johns'),
(25, '(GMT-03:00) Brasilia ', 'America/Sao_Paulo'),
(26, '(GMT-03:00) Buenos Aires ', 'America/Argentina/Buenos_Aires'),
(27, '(GMT-03:00) Georgetown ', 'America/Argentina/Buenos_Aires'),
(28, '(GMT-03:00) Greenland ', 'America/Godthab'),
(29, '(GMT-02:00) Mid-Atlantic ', 'America/Noronha'),
(30, '(GMT-01:00) Azores ', 'Atlantic/Azores'),
(31, '(GMT-01:00) Cape Verde Is. ', 'Atlantic/Cape_Verde'),
(32, '(GMT+00:00) Casablanca ', 'Africa/Casablanca'),
(33, '(GMT+00:00) Edinburgh ', 'Europe/London'),
(34, '(GMT+00:00) Dublin ', 'Europe/Dublin'),
(35, '(GMT+00:00) Lisbon ', 'Europe/Lisbon'),
(36, '(GMT+00:00) London ', 'Europe/London'),
(37, '(GMT+00:00) Monrovia ', 'Africa/Monrovia'),
(38, '(GMT+00:00) UTC ', 'UTC'),
(39, '(GMT+01:00) Amsterdam ', 'Europe/Amsterdam'),
(40, '(GMT+01:00) Belgrade ', 'Europe/Belgrade'),
(41, '(GMT+01:00) Berlin ', 'Europe/Berlin'),
(42, '(GMT+01:00) Bern ', 'Europe/Berlin'),
(43, '(GMT+01:00) Bratislava ', 'Europe/Bratislava'),
(44, '(GMT+01:00) Brussels ', 'Europe/Brussels'),
(45, '(GMT+01:00) Budapest ', 'Europe/Budapest'),
(46, '(GMT+01:00) Copenhagen ', 'Europe/Copenhagen'),
(47, '(GMT+01:00) Ljubljana ', 'Europe/Ljubljana'),
(48, '(GMT+01:00) Madrid ', 'Europe/Madrid'),
(49, '(GMT+01:00) Paris ', 'Europe/Paris'),
(50, '(GMT+01:00) Prague ', 'Europe/Prague'),
(51, '(GMT+01:00) Rome ', 'Europe/Rome'),
(52, '(GMT+01:00) Sarajevo ', 'Europe/Sarajevo'),
(53, '(GMT+01:00) Skopje ', 'Europe/Skopje'),
(54, '(GMT+01:00) Stockholm ', 'Europe/Stockholm'),
(55, '(GMT+01:00) Vienna ', 'Europe/Vienna'),
(56, '(GMT+01:00) Warsaw ', 'Europe/Warsaw'),
(57, '(GMT+01:00) West Central Africa ', 'Africa/Lagos'),
(58, '(GMT+01:00) Zagreb ', 'Europe/Zagreb'),
(59, '(GMT+02:00) Athens ', 'Europe/Athens'),
(60, '(GMT+02:00) Bucharest ', 'Europe/Bucharest'),
(61, '(GMT+02:00) Cairo ', 'Africa/Cairo'),
(62, '(GMT+02:00) Harare ', 'Africa/Harare'),
(63, '(GMT+02:00) Helsinki ', 'Europe/Helsinki'),
(64, '(GMT+02:00) Istanbul ', 'Europe/Istanbul'),
(65, '(GMT+02:00) Jerusalem ', 'Asia/Jerusalem'),
(66, '(GMT+02:00) Kyiv ', 'Europe/Helsinki'),
(67, '(GMT+02:00) Pretoria ', 'Africa/Johannesburg'),
(68, '(GMT+02:00) Riga ', 'Europe/Riga'),
(69, '(GMT+02:00) Sofia ', 'Europe/Sofia'),
(70, '(GMT+02:00) Tallinn ', 'Europe/Tallinn'),
(71, '(GMT+02:00) Vilnius ', 'Europe/Vilnius'),
(72, '(GMT+03:00) Baghdad ', 'Asia/Baghdad'),
(73, '(GMT+03:00) Kuwait ', 'Asia/Kuwait'),
(74, '(GMT+03:00) Minsk ', 'Europe/Minsk'),
(75, '(GMT+03:00) Nairobi ', 'Africa/Nairobi'),
(76, '(GMT+03:00) Riyadh ', 'Asia/Riyadh'),
(77, '(GMT+03:00) Volgograd ', 'Europe/Volgograd'),
(78, '(GMT+03:30) Tehran ', 'Asia/Tehran'),
(79, '(GMT+04:00) Abu Dhabi ', 'Asia/Muscat'),
(80, '(GMT+04:00) Baku ', 'Asia/Baku'),
(81, '(GMT+04:00) Moscow ', 'Europe/Moscow'),
(82, '(GMT+04:00) Muscat ', 'Asia/Muscat'),
(83, '(GMT+04:00) St. Petersburg ', 'Europe/Moscow'),
(84, '(GMT+04:00) Tbilisi ', 'Asia/Tbilisi'),
(85, '(GMT+04:00) Yerevan ', 'Asia/Yerevan'),
(86, '(GMT+04:30) Kabul ', 'Asia/Kabul'),
(87, '(GMT+05:00) Islamabad ', 'Asia/Karachi'),
(88, '(GMT+05:00) Karachi ', 'Asia/Karachi'),
(89, '(GMT+05:00) Tashkent ', 'Asia/Tashkent'),
(90, '(GMT+05:30) Chennai ', 'Asia/Calcutta'),
(91, '(GMT+05:30) Kolkata ', 'Asia/Kolkata'),
(92, '(GMT+05:30) Mumbai ', 'Asia/Calcutta'),
(93, '(GMT+05:30) New Delhi ', 'Asia/Calcutta'),
(94, '(GMT+05:30) Sri Jayawardenepura ', 'Asia/Calcutta'),
(95, '(GMT+05:45) Kathmandu ', 'Asia/Katmandu'),
(96, '(GMT+06:00) Almaty ', 'Asia/Almaty'),
(97, '(GMT+06:00) Astana ', 'Asia/Dhaka'),
(98, '(GMT+06:00) Dhaka ', 'Asia/Dhaka'),
(99, '(GMT+06:00) Ekaterinburg ', 'Asia/Yekaterinburg'),
(100, '(GMT+06:30) Rangoon ', 'Asia/Rangoon'),
(101, '(GMT+07:00) Bangkok ', 'Asia/Bangkok'),
(102, '(GMT+07:00) Hanoi ', 'Asia/Bangkok'),
(103, '(GMT+07:00) Jakarta ', 'Asia/Jakarta'),
(104, '(GMT+07:00) Novosibirsk ', 'Asia/Novosibirsk'),
(105, '(GMT+08:00) Beijing ', 'Asia/Hong_Kong'),
(106, '(GMT+08:00) Chongqing ', 'Asia/Chongqing'),
(107, '(GMT+08:00) Hong Kong ', 'Asia/Hong_Kong'),
(108, '(GMT+08:00) Krasnoyarsk ', 'Asia/Krasnoyarsk'),
(109, '(GMT+08:00) Kuala Lumpur ', 'Asia/Kuala_Lumpur'),
(110, '(GMT+08:00) Perth ', 'Australia/Perth'),
(111, '(GMT+08:00) Singapore ', 'Asia/Singapore'),
(112, '(GMT+08:00) Taipei ', 'Asia/Taipei'),
(113, '(GMT+08:00) Ulaan Bataar ', 'Asia/Ulan_Bator'),
(114, '(GMT+08:00) Urumqi ', 'Asia/Urumqi'),
(115, '(GMT+09:00) Irkutsk ', 'Asia/Irkutsk'),
(116, '(GMT+09:00) Osaka ', 'Asia/Tokyo'),
(117, '(GMT+09:00) Sapporo ', 'Asia/Tokyo'),
(118, '(GMT+09:00) Seoul ', 'Asia/Seoul'),
(119, '(GMT+09:00) Tokyo ', 'Asia/Tokyo'),
(120, '(GMT+09:30) Adelaide ', 'Australia/Adelaide'),
(121, '(GMT+09:30) Darwin ', 'Australia/Darwin'),
(122, '(GMT+10:00) Brisbane ', 'Australia/Brisbane'),
(123, '(GMT+10:00) Canberra ', 'Australia/Canberra'),
(124, '(GMT+10:00) Guam ', 'Pacific/Guam'),
(125, '(GMT+10:00) Hobart ', 'Australia/Hobart'),
(126, '(GMT+10:00) Melbourne ', 'Australia/Melbourne'),
(127, '(GMT+10:00) Port Moresby ', 'Pacific/Port_Moresby'),
(128, '(GMT+10:00) Sydney ', 'Australia/Sydney'),
(129, '(GMT+10:00) Yakutsk ', 'Asia/Yakutsk'),
(130, '(GMT+11:00) Vladivostok ', 'Asia/Vladivostok'),
(131, '(GMT+12:00) Auckland ', 'Pacific/Auckland'),
(132, '(GMT+12:00) Fiji ', 'Pacific/Fiji'),
(133, '(GMT+12:00) International Date Line West ', 'Pacific/Kwajalein'),
(134, '(GMT+12:00) Kamchatka ', 'Asia/Kamchatka'),
(135, '(GMT+12:00) Magadan ', 'Asia/Magadan'),
(136, '(GMT+12:00) Marshall Is. ', 'Pacific/Fiji'),
(137, '(GMT+12:00) New Caledonia ', 'Asia/Magadan'),
(138, '(GMT+12:00) Solomon Is. ', 'Asia/Magadan'),
(139, '(GMT+12:00) Wellington ', 'Pacific/Auckland'),
(140, '(GMT+13:00) Nuku\\alofa ', 'Pacific/Tongatapu');

/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;

Aqui está um que cria uma matriz multidimensional classificada por deslocamento e nome legal:

function timezones() {
    $timezones = [];

    foreach (timezone_identifiers_list() as $timezone) {
        $datetime = new \DateTime('now', new DateTimeZone($timezone));
        $timezones[] = [
            'sort' => str_replace(':', '', $datetime->format('P')),
            'offset' => $datetime->format('P'),
            'name' => str_replace('_', ' ', implode(', ', explode('/', $timezone))),
            'timezone' => $timezone,
        ];
    }

    usort($timezones, function($a, $b) {
        return $a['sort'] - $b['sort'] ?: strcmp($a['name'], $b['name']);
    });

    return $timezones;
}

foreach (timezones() as $timezone) {
    echo '(UTC '.$timezone['offset'].') '.$timezone['name'].'<br>';
}

Echos:

(UTC -11:00) Pacific, Midway
(UTC -11:00) Pacific, Niue
(UTC -11:00) Pacific, Pago Pago
(UTC -10:00) Pacific, Honolulu
(UTC -10:00) Pacific, Johnston
(UTC -10:00) Pacific, Rarotonga
(UTC -10:00) Pacific, Tahiti
(UTC -09:30) Pacific, Marquesas
(UTC -09:00) America, Adak
(UTC -09:00) Pacific, Gambier
(UTC -08:00) America, Anchorage
(UTC -08:00) America, Juneau
...

$timezone = array(
    'Pacific/Midway' => '(GMT-11:00) Midway Island, Samoa',
    'America/Adak' => '(GMT-10:00) Hawaii-Aleutian',
    'Etc/GMT+10' => '(GMT-10:00) Hawaii',
    'Pacific/Marquesas' => '(GMT-09:30) Marquesas Islands',
    'Pacific/Gambier' => '(GMT-09:00) Gambier Islands',
    'America/Anchorage' => '(GMT-09:00) Alaska',
    'America/Ensenada' => '(GMT-08:00) Tijuana, Baja California',
    'Etc/GMT+8' => '(GMT-08:00) Pitcairn Islands',
    'America/Los_Angeles' => '(GMT-08:00) Pacific Time (US & Canada)',
    'America/Denver' => '(GMT-07:00) Mountain Time (US & Canada)',
    'America/Chihuahua' => '(GMT-07:00) Chihuahua, La Paz, Mazatlan',
    'America/Dawson_Creek' => '(GMT-07:00) Arizona',
    'America/Belize' => '(GMT-06:00) Saskatchewan, Central America',
    'America/Cancun' => '(GMT-06:00) Guadalajara, Mexico City, Monterrey',
    'Chile/EasterIsland' => '(GMT-06:00) Easter Island',
    'America/Chicago' => '(GMT-06:00) Central Time (US & Canada)',
    'America/New_York' => '(GMT-05:00) Eastern Time (US & Canada)',
    'America/Havana' => '(GMT-05:00) Cuba',
    'America/Bogota' => '(GMT-05:00) Bogota, Lima, Quito, Rio Branco',
    'America/Caracas' => '(GMT-04:30) Caracas',
    'America/Santiago' => '(GMT-04:00) Santiago',
    'America/La_Paz' => '(GMT-04:00) La Paz',
    'Atlantic/Stanley' => '(GMT-04:00) Faukland Islands',
    'America/Campo_Grande' => '(GMT-04:00) Brazil',
    'America/Goose_Bay' => '(GMT-04:00) Atlantic Time (Goose Bay)',
    'America/Glace_Bay' => '(GMT-04:00) Atlantic Time (Canada)',
    'America/St_Johns' => '(GMT-03:30) Newfoundland',
    'America/Araguaina' => '(GMT-03:00) UTC-3',
    'America/Montevideo' => '(GMT-03:00) Montevideo',
    'America/Miquelon' => '(GMT-03:00) Miquelon, St. Pierre',
    'America/Godthab' => '(GMT-03:00) Greenland',
    'America/Argentina/Buenos_Aires' => '(GMT-03:00) Buenos Aires',
    'America/Sao_Paulo' => '(GMT-03:00) Brasilia',
    'America/Noronha' => '(GMT-02:00) Mid-Atlantic',
    'Atlantic/Cape_Verde' => '(GMT-01:00) Cape Verde Is.',
    'Atlantic/Azores' => '(GMT-01:00) Azores',
    'Europe/Belfast' => '(GMT) Greenwich Mean Time : Belfast',
    'Europe/Dublin' => '(GMT) Greenwich Mean Time : Dublin',
    'Europe/Lisbon' => '(GMT) Greenwich Mean Time : Lisbon',
    'Europe/London' => '(GMT) Greenwich Mean Time : London',
    'Africa/Abidjan' => '(GMT) Monrovia, Reykjavik',
    'Europe/Amsterdam' => '(GMT+01:00) Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna',
    'Europe/Belgrade' => '(GMT+01:00) Belgrade, Bratislava, Budapest, Ljubljana, Prague',
    'Europe/Brussels' => '(GMT+01:00) Brussels, Copenhagen, Madrid, Paris',
    'Africa/Algiers' => '(GMT+01:00) West Central Africa',
    'Africa/Windhoek' => '(GMT+01:00) Windhoek',
    'Asia/Beirut' => '(GMT+02:00) Beirut',
    'Africa/Cairo' => '(GMT+02:00) Cairo',
    'Asia/Gaza' => '(GMT+02:00) Gaza',
    'Africa/Blantyre' => '(GMT+02:00) Harare, Pretoria',
    'Asia/Jerusalem' => '(GMT+02:00) Jerusalem',
    'Europe/Minsk' => '(GMT+02:00) Minsk',
    'Asia/Damascus' => '(GMT+02:00) Syria',
    'Europe/Moscow' => '(GMT+03:00) Moscow, St. Petersburg, Volgograd',
    'Africa/Addis_Ababa' => '(GMT+03:00) Nairobi',
    'Asia/Tehran' => '(GMT+03:30) Tehran',
    'Asia/Dubai' => '(GMT+04:00) Abu Dhabi, Muscat',
    'Asia/Yerevan' => '(GMT+04:00) Yerevan',
    'Asia/Kabul' => '(GMT+04:30) Kabul',
    'Asia/Yekaterinburg' => '(GMT+05:00) Ekaterinburg',
    'Asia/Tashkent' => '(GMT+05:00) Tashkent',
    'Asia/Kolkata' => '(GMT+05:30) Chennai, Kolkata, Mumbai, New Delhi',
    'Asia/Katmandu' => '(GMT+05:45) Kathmandu',
    'Asia/Dhaka' => '(GMT+06:00) Astana, Dhaka',
    'Asia/Novosibirsk' => '(GMT+06:00) Novosibirsk',
    'Asia/Rangoon' => '(GMT+06:30) Yangon (Rangoon)',
    'Asia/Bangkok' => '(GMT+07:00) Bangkok, Hanoi, Jakarta',
    'Asia/Krasnoyarsk' => '(GMT+07:00) Krasnoyarsk',
    'Asia/Hong_Kong' => '(GMT+08:00) Beijing, Chongqing, Hong Kong, Urumqi',
    'Asia/Irkutsk' => '(GMT+08:00) Irkutsk, Ulaan Bataar',
    'Australia/Perth' => '(GMT+08:00) Perth',
    'Australia/Eucla' => '(GMT+08:45) Eucla',
    'Asia/Tokyo' => '(GMT+09:00) Osaka, Sapporo, Tokyo',
    'Asia/Seoul' => '(GMT+09:00) Seoul',
    'Asia/Yakutsk' => '(GMT+09:00) Yakutsk',
    'Australia/Adelaide' => '(GMT+09:30) Adelaide',
    'Australia/Darwin' => '(GMT+09:30) Darwin',
    'Australia/Brisbane' => '(GMT+10:00) Brisbane',
    'Australia/Hobart' => '(GMT+10:00) Hobart',
    'Asia/Vladivostok' => '(GMT+10:00) Vladivostok',
    'Australia/Lord_Howe' => '(GMT+10:30) Lord Howe Island',
    'Etc/GMT-11' => '(GMT+11:00) Solomon Is., New Caledonia',
    'Asia/Magadan' => '(GMT+11:00) Magadan',
    'Pacific/Norfolk' => '(GMT+11:30) Norfolk Island',
    'Asia/Anadyr' => '(GMT+12:00) Anadyr, Kamchatka',
    'Pacific/Auckland' => '(GMT+12:00) Auckland, Wellington',
    'Etc/GMT-12' => '(GMT+12:00) Fiji, Kamchatka, Marshall Is.',
    'Pacific/Chatham' => '(GMT+12:45) Chatham Islands',
    'Pacific/Tongatapu' => '(GMT+13:00) Nukualofa',
    'Pacific/Kiritimati' => '(GMT+14:00) Kiritimati',

date_default_timezone_set($timezone);

O uso de listAbbreviations () não faz sentido, pois em todas as áreas ele retorna todos os diferentes deslocamentos que foram historicamente usados ​​ali, não apenas os atuais. A fonte base correta da lista é definitivamente listIdentifiers ().

Eu geraria a lista apenas uma vez e a salvaria para evitar gerá-la para cada solicitação. Eu poderia atualizá-lo uma vez por mês.

Além disso, eu poderia colocar todas as informações de fuso horário em um script js separado e gerar a própria lista de seleção no lado do cliente. O script js também pode ser armazenado em cache, os fusos horários não mudam frequentemente.

Além disso, usando javascript no lado do cliente, você pode saber a hora local atual e, portanto, pode encontrar as zonas que possuem a mesma hora agora (os minutos podem ser diferentes, portanto a comparação deve ser aproximada) e exibi-los na parte superior do lista, para que o usuário não precise rolar por todos os 400 itens. Você também pode exibir as zonas adjacentes (+/- 1 hora) a seguir.

Sei que isso já tem uma resposta, mas vi uma oportunidade de melhorar uma das respostas aqui. Toland H postou um código muito bom que faz exatamente o que a pergunta estava pedindo. Abaixo está uma versão abreviada e expandida do código de Toland H:

• A função coloca tudo em tags de opção para você. Apenas faça eco do retorno entre as tags selecionadas.
• Melhorias importantes: a lista é classificada primeiro por continente e organizada em grupos de opções com base em continentes. Torna muito amigável para os visitantes que escolhem seu fuso horário.

function generate_timezone_list() {
static $allRegions = array(
DateTimeZone::AFRICA,
DateTimeZone::AMERICA,
DateTimeZone::ANTARCTICA,
DateTimeZone::ASIA,
DateTimeZone::ATLANTIC,
DateTimeZone::AUSTRALIA,
DateTimeZone::EUROPE,
DateTimeZone::INDIAN,
DateTimeZone::PACIFIC
);
// Makes it easier to create option groups next
$list = array ('AFRICA','AMERICA','ANTARCTICA','ASIA','ATLANTIC','AUSTRALIA','EUROPE','INDIAN','PACIFIC');
// Make array holding the regions (continents), they are arrays w/ all their cities
$region = array();
foreach ($allRegions as $area){
array_push ($region,DateTimeZone::listIdentifiers( $area ));
}   
$count = count ($region); $i = 0; $holder = '';
// Go through each region one by one, sorting and formatting it's cities
while ($i < $count){
$chunck = $region[$i];
// Create the region (continents) option group
$holder .= '<optgroup label="---------- '.$list[$i].' ----------">';
$timezone_offsets = array();
foreach( $chunck as $timezone ){
$tz = new DateTimeZone($timezone);
$timezone_offsets[$timezone] = $tz->getOffset(new DateTime);
}
asort ($timezone_offsets);
$timezone_list = array();
foreach ($timezone_offsets as $timezone => $offset){
$offset_prefix = $offset < 0 ? '-' : '+';
$offset_formatted = gmdate( 'H:i', abs($offset) );
$pretty_offset = "UTC ${offset_prefix}${offset_formatted}";
$timezone_list[$timezone] = "(${pretty_offset}) $timezone";     
}
// All the formatting is done, finish and move on to next region
foreach ($timezone_list as $key => $val){
$holder .= '<option value="'.$key.'">'.$val.'</option>';
}
$holder .= '</optgroup>';
++$i;
}
return $holder;
}
echo "<select>".generate_timezone_list()."</select>";

Então tudo que você precisa fazer é repetir o que é retornado entre as tags de seleção html. Você receberá uma lista de seleção mais ou menos assim:

----- AFRICA -----
(UTC +00:00) Africa/ city name
(UTC +01:00) Africa/ city name
(UTC +02:00) Africa/ city name
(UTC +02:00) Africa/ city name
----- AMERICA -----
(UTC -09:00) America/ city name
(UTC -07:00) America/ city name
(UTC +02:00) America/ city name
(UTC +05:00) America/ city name

E assim por diante...

Esta função PHP faz o trabalho para você e devolve uma matriz:

function time_zonelist(){
    $return = array();
    $timezone_identifiers_list = timezone_identifiers_list();
    foreach($timezone_identifiers_list as $timezone_identifier){
        $date_time_zone = new DateTimeZone($timezone_identifier);
        $date_time = new DateTime('now', $date_time_zone);
        $hours = floor($date_time_zone->getOffset($date_time) / 3600);
        $mins = floor(($date_time_zone->getOffset($date_time) - ($hours*3600)) / 60);
        $hours = 'GMT' . ($hours < 0 ? $hours : '+'.$hours);
        $mins = ($mins > 0 ? $mins : '0'.$mins);
        $text = str_replace("_"," ",$timezone_identifier);
        $return[$timezone_identifier] = $text.' ('.$hours.':'.$mins.')';
    }
    return $return;
}

Esta função PHP retorna uma matriz de todos os fusos horários existentes, incluindo Offset:

Use-o, por exemplo:

print_r(time_zonelist());

Eu queria ter algo mais simples para meus usuários, da maneira que o Google faz ..

$timezones = [
    "AF" => [
        "name" => "Afghanistan" 
    ],
    "AL" => [
        "name" => "Albania" 
    ],
    "DZ" => [
        "name" => "Algeria" 
    ],
    "AS" => [
        "name" => "American Samoa" 
    ],
    "AD" => [
        "name" => "Andorra" 
    ],
    "AQ" => [
        "name" => "Antarctica" 
    ],
    "AG" => [
        "name" => "Antigua & Barbuda" 
    ],
    "AR" => [
        "name" => "Argentina" 
    ],
    "AM" => [
        "name" => "Armenia" 
    ],
    "AU" => [
        "name" => "Australia" 
    ],
    "AT" => [
        "name" => "Austria" 
    ],
    "AZ" => [
        "name" => "Azerbaijan" 
    ],
    "BS" => [
        "name" => "Bahamas" 
    ],
    "BD" => [
        "name" => "Bangladesh" 
    ],
    "BB" => [
        "name" => "Barbados" 
    ],
    "BY" => [
        "name" => "Belarus" 
    ],
    "BE" => [
        "name" => "Belgium" 
    ],
    "BZ" => [
        "name" => "Belize" 
    ],
    "BM" => [
        "name" => "Bermuda" 
    ],
    "BT" => [
        "name" => "Bhutan" 
    ],
    "BO" => [
        "name" => "Bolivia" 
    ],
    "BA" => [
        "name" => "Bosnia & Herzegovina" 
    ],
    "BR" => [
        "name" => "Brazil" 
    ],
    "IO" => [
        "name" => "British Indian Ocean Territory" 
    ],
    "BN" => [
        "name" => "Brunei" 
    ],
    "BG" => [
        "name" => "Bulgaria" 
    ],
    "CA" => [
        "name" => "Canada" 
    ],
    "CV" => [
        "name" => "Cape Verde" 
    ],
    "KY" => [
        "name" => "Cayman Islands" 
    ],
    "TD" => [
        "name" => "Chad" 
    ],
    "CL" => [
        "name" => "Chile" 
    ],
    "CN" => [
        "name" => "China" 
    ],
    "CX" => [
        "name" => "Christmas Island" 
    ],
    "CC" => [
        "name" => "Cocos (Keeling) Islands" 
    ],
    "CO" => [
        "name" => "Colombia" 
    ],
    "CK" => [
        "name" => "Cook Islands" 
    ],
    "CR" => [
        "name" => "Costa Rica" 
    ],
    "CI" => [
        "name" => "Côte d’Ivoire" 
    ],
    "HR" => [
        "name" => "Croatia" 
    ],
    "CU" => [
        "name" => "Cuba" 
    ],
    "CW" => [
        "name" => "Curaçao" 
    ],
    "CY" => [
        "name" => "Cyprus" 
    ],
    "CZ" => [
        "name" => "Czech Republic" 
    ],
    "DK" => [
        "name" => "Denmark" 
    ],
    "DO" => [
        "name" => "Dominican Republic" 
    ],
    "EC" => [
        "name" => "Ecuador" 
    ],
    "EG" => [
        "name" => "Egypt" 
    ],
    "SV" => [
        "name" => "El Salvador" 
    ],
    "EE" => [
        "name" => "Estonia" 
    ],
    "FK" => [
        "name" => "Falkland Islands (Islas Malvinas)" 
    ],
    "FO" => [
        "name" => "Faroe Islands" 
    ],
    "FJ" => [
        "name" => "Fiji" 
    ],
    "FI" => [
        "name" => "Finland" 
    ],
    "FR" => [
        "name" => "France" 
    ],
    "GF" => [
        "name" => "French Guiana" 
    ],
    "PF" => [
        "name" => "French Polynesia" 
    ],
    "TF" => [
        "name" => "French Southern Territories" 
    ],
    "GE" => [
        "name" => "Georgia" 
    ],
    "DE" => [
        "name" => "Germany" 
    ],
    "GH" => [
        "name" => "Ghana" 
    ],
    "GI" => [
        "name" => "Gibraltar" 
    ],
    "GR" => [
        "name" => "Greece" 
    ],
    "GL" => [
        "name" => "Greenland" 
    ],
    "GU" => [
        "name" => "Guam" 
    ],
    "GT" => [
        "name" => "Guatemala" 
    ],
    "GW" => [
        "name" => "Guinea-Bissau" 
    ],
    "GY" => [
        "name" => "Guyana" 
    ],
    "HT" => [
        "name" => "Haiti" 
    ],
    "HN" => [
        "name" => "Honduras" 
    ],
    "HK" => [
        "name" => "Hong Kong" 
    ],
    "HU" => [
        "name" => "Hungary" 
    ],
    "IS" => [
        "name" => "Iceland" 
    ],
    "IN" => [
        "name" => "India" 
    ],
    "ID" => [
        "name" => "Indonesia" 
    ],
    "IR" => [
        "name" => "Iran" 
    ],
    "IQ" => [
        "name" => "Iraq" 
    ],
    "IE" => [
        "name" => "Ireland" 
    ],
    "IL" => [
        "name" => "Israel" 
    ],
    "IT" => [
        "name" => "Italy" 
    ],
    "JM" => [
        "name" => "Jamaica" 
    ],
    "JP" => [
        "name" => "Japan" 
    ],
    "JO" => [
        "name" => "Jordan" 
    ],
    "KZ" => [
        "name" => "Kazakhstan" 
    ],
    "KE" => [
        "name" => "Kenya" 
    ],
    "KI" => [
        "name" => "Kiribati" 
    ],
    "KG" => [
        "name" => "Kyrgyzstan" 
    ],
    "LV" => [
        "name" => "Latvia" 
    ],
    "LB" => [
        "name" => "Lebanon" 
    ],
    "LR" => [
        "name" => "Liberia" 
    ],
    "LY" => [
        "name" => "Libya" 
    ],
    "LT" => [
        "name" => "Lithuania" 
    ],
    "LU" => [
        "name" => "Luxembourg" 
    ],
    "MO" => [
        "name" => "Macau" 
    ],
    "MK" => [
        "name" => "Macedonia (FYROM)" 
    ],
    "MY" => [
        "name" => "Malaysia" 
    ],
    "MV" => [
        "name" => "Maldives" 
    ],
    "MT" => [
        "name" => "Malta" 
    ],
    "MH" => [
        "name" => "Marshall Islands" 
    ],
    "MQ" => [
        "name" => "Martinique" 
    ],
    "MU" => [
        "name" => "Mauritius" 
    ],
    "MX" => [
        "name" => "Mexico" 
    ],
    "FM" => [
        "name" => "Micronesia" 
    ],
    "MD" => [
        "name" => "Moldova" 
    ],
    "MC" => [
        "name" => "Monaco" 
    ],
    "MN" => [
        "name" => "Mongolia" 
    ],
    "MA" => [
        "name" => "Morocco" 
    ],
    "MZ" => [
        "name" => "Mozambique" 
    ],
    "MM" => [
        "name" => "Myanmar (Burma)" 
    ],
    "NA" => [
        "name" => "Namibia" 
    ],
    "NR" => [
        "name" => "Nauru" 
    ],
    "NP" => [
        "name" => "Nepal" 
    ],
    "NL" => [
        "name" => "Netherlands" 
    ],
    "NC" => [
        "name" => "New Caledonia" 
    ],
    "NZ" => [
        "name" => "New Zealand" 
    ],
    "NI" => [
        "name" => "Nicaragua" 
    ],
    "NG" => [
        "name" => "Nigeria" 
    ],
    "NU" => [
        "name" => "Niue" 
    ],
    "NF" => [
        "name" => "Norfolk Island" 
    ],
    "KP" => [
        "name" => "North Korea" 
    ],
    "MP" => [
        "name" => "Northern Mariana Islands" 
    ],
    "NO" => [
        "name" => "Norway" 
    ],
    "PK" => [
        "name" => "Pakistan" 
    ],
    "PW" => [
        "name" => "Palau" 
    ],
    "PS" => [
        "name" => "Palestine" 
    ],
    "PA" => [
        "name" => "Panama" 
    ],
    "PG" => [
        "name" => "Papua New Guinea" 
    ],
    "PY" => [
        "name" => "Paraguay" 
    ],
    "PE" => [
        "name" => "Peru" 
    ],
    "PH" => [
        "name" => "Philippines" 
    ],
    "PN" => [
        "name" => "Pitcairn Islands" 
    ],
    "PL" => [
        "name" => "Poland" 
    ],
    "PT" => [
        "name" => "Portugal" 
    ],
    "PR" => [
        "name" => "Puerto Rico" 
    ],
    "QA" => [
        "name" => "Qatar" 
    ],
    "RE" => [
        "name" => "Réunion" 
    ],
    "RO" => [
        "name" => "Romania" 
    ],
    "RU" => [
        "name" => "Russia" 
    ],
    "WS" => [
        "name" => "Samoa" 
    ],
    "SM" => [
        "name" => "San Marino" 
    ],
    "SA" => [
        "name" => "Saudi Arabia" 
    ],
    "RS" => [
        "name" => "Serbia" 
    ],
    "SC" => [
        "name" => "Seychelles" 
    ],
    "SG" => [
        "name" => "Singapore" 
    ],
    "SK" => [
        "name" => "Slovakia" 
    ],
    "SI" => [
        "name" => "Slovenia" 
    ],
    "SB" => [
        "name" => "Solomon Islands" 
    ],
    "ZA" => [
        "name" => "South Africa" 
    ],
    "GS" => [
        "name" => "South Georgia & South Sandwich Islands" 
    ],
    "KR" => [
        "name" => "South Korea" 
    ],
    "ES" => [
        "name" => "Spain" 
    ],
    "LK" => [
        "name" => "Sri Lanka" 
    ],
    "PM" => [
        "name" => "St. Pierre & Miquelon" 
    ],
    "SD" => [
        "name" => "Sudan" 
    ],
    "SR" => [
        "name" => "Suriname" 
    ],
    "SJ" => [
        "name" => "Svalbard & Jan Mayen" 
    ],
    "SE" => [
        "name" => "Sweden" 
    ],
    "CH" => [
        "name" => "Switzerland" 
    ],
    "SY" => [
        "name" => "Syria" 
    ],
    "TW" => [
        "name" => "Taiwan" 
    ],
    "TJ" => [
        "name" => "Tajikistan" 
    ],
    "TH" => [
        "name" => "Thailand" 
    ],
    "TL" => [
        "name" => "Timor-Leste" 
    ],
    "TK" => [
        "name" => "Tokelau" 
    ],
    "TO" => [
        "name" => "Tonga" 
    ],
    "TT" => [
        "name" => "Trinidad & Tobago" 
    ],
    "TN" => [
        "name" => "Tunisia" 
    ],
    "TR" => [
        "name" => "Turkey" 
    ],
    "TM" => [
        "name" => "Turkmenistan" 
    ],
    "TC" => [
        "name" => "Turks & Caicos Islands" 
    ],
    "TV" => [
        "name" => "Tuvalu" 
    ],
    "UM" => [
        "name" => "U.S. Outlying Islands" 
    ],
    "UA" => [
        "name" => "Ukraine" 
    ],
    "AE" => [
        "name" => "United Arab Emirates" 
    ],
    "GB" => [
        "name" => "United Kingdom" 
    ],
    "US" => [
        "name" => "United States" 
    ],
    "UY" => [
        "name" => "Uruguay" 
    ],
    "UZ" => [
        "name" => "Uzbekistan" 
    ],
    "VU" => [
        "name" => "Vanuatu" 
    ],
    "VA" => [
        "name" => "Vatican City" 
    ],
    "VE" => [
        "name" => "Venezuela" 
    ],
    "VN" => [
        "name" => "Vietnam" 
    ],
    "WF" => [
        "name" => "Wallis & Futuna" 
    ],
    "EH" => [
        "name" => "Western Sahara" 
    ],
];

// taken from Toland Hon's Answer
function prettyOffset($offset) {
    $offset_prefix = $offset < 0 ? '-' : '+';
    $offset_formatted = gmdate( 'H:i', abs($offset) );

    $pretty_offset = "UTC${offset_prefix}${offset_formatted}";

    return $pretty_offset;
}

foreach ($timezones as $k => $v) {
    $tz = DateTimeZone::listIdentifiers(DateTimeZone::PER_COUNTRY, $k);

    foreach ($tz as $value) {
        $t = new DateTimeZone($value);
        $offset = (new DateTime("now", $t))->getOffset();
        $timezones[$k]['timezones'][$value] = prettyOffset($offset);
    }   
}