Generating a drop down list of timezones with PHP

Question

Most sites need some way to show the dates on the site in the users preferred timezone. Below are two lists that I found and then one method using the built in PHP DateTime class in PHP 5.

I need help knowing which of these would be the best to attempt to use when trying to get the UTC offset from the user on register.

One:

<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>

Or using PHP friendly values:

<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>

Or just using PHP itself:

$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 );

It seems like the last one would be the safest as it would grow with the PHP release being used. You could also flip that array around when needed to tie timezones to city names.

Answer 1

After trying all solutions presented here and not being satisfied, I have found a script which is matching my needs and it is more user friendly. For the record, I will save it as a possible solution. I love the copy/paste solutions :)

Script returns a select with whatever timezone you want preselected.

Source: https://e-tel.eu/2011/07/13/create-a-time-zone-drop-down-list-ddl-in-php/

<?php
/**
 * returns a HTML formated TimeZone select
 *
 * PHP 5 >= 5.2.0
 * 
 * @param $selectedTimeZone string The timezone marked as "selected"
 * @return string
 */
function displayTimeZoneSelect($selectedTimeZone = 'America/New_York'){
    $countryCodes = getCountryCodes();
    $return = null;
    foreach ($countryCodes as $country => $countryCode) {
        $timezone_identifiers = DateTimeZone::listIdentifiers(DateTimeZone::PER_COUNTRY,$countryCode);
        foreach( $timezone_identifiers as $value ){
            /* getTimeZoneOffset returns minutes and we need to display hours */
            $offset = getTimeZoneOffset($value)/60;
            /* for the GMT+1 GMT-1 display */
            $offset = ( substr($offset,0,1) == "-" ? " (GMT" : " (GMT+" ) . $offset . ")";
            /* America/New_York -> America/New York */
            $displayValue = (str_replace('_',' ',$value));
            /* Find the city */
            $ex = explode("/",$displayValue);
            $city = ( ($ex[2]) ? $ex[2] : $ex[1] );
            /* For the special names */
            $displayValue = htmlentities($country." - ".$city.$offset); 
            /* handle the $selectedTimeZone in the select form */
            $selected = ( ($value == $selectedTimeZone) ? ' selected="selected"' : null );
            $return .= '<option value="' . $value . '"' . $selected . '>'
                . $displayValue
                . '</option>' . PHP_EOL;
        }
    }

    return $return;
}

/**
 * ISO 3166 code list
 *
 * @return array The country codes in 'COUNTRY' => 'CODE' format
 * @link http://www.iso.org/iso/iso_3166_code_lists ISO Website
 */
function getCountryCodes(){
$return = array(
"AFGHANISTAN"=>"AF",
"ALAND ISLANDS"=>"AX",
"ALBANIA"=>"AL",
"ALGERIA"=>"DZ",
"AMERICAN SAMOA"=>"AS",
"ANDORRA"=>"AD",
"ANGOLA"=>"AO",
"ANGUILLA"=>"AI",
"ANTARCTICA"=>"AQ",
"ANTIGUA AND BARBUDA"=>"AG",
"ARGENTINA"=>"AR",
"ARMENIA"=>"AM",
"ARUBA"=>"AW",
"AUSTRALIA"=>"AU",
"AUSTRIA"=>"AT",
"AZERBAIJAN"=>"AZ",
"BAHAMAS"=>"BS",
"BAHRAIN"=>"BH",
"BANGLADESH"=>"BD",
"BARBADOS"=>"BB",
"BELARUS"=>"BY",
"BELGIUM"=>"BE",
"BELIZE"=>"BZ",
"BENIN"=>"BJ",
"BERMUDA"=>"BM",
"BHUTAN"=>"BT",
"BOLIVIA, PLURINATIONAL STATE OF"=>"BO",
"BONAIRE, SINT EUSTATIUS AND SABA"=>"BQ",
"BOSNIA AND HERZEGOVINA"=>"BA",
"BOTSWANA"=>"BW",
"BOUVET ISLAND"=>"BV",
"BRAZIL"=>"BR",
"BRITISH INDIAN OCEAN TERRITORY"=>"IO",
"BRUNEI DARUSSALAM"=>"BN",
"BULGARIA"=>"BG",
"BURKINA FASO"=>"BF",
"BURUNDI"=>"BI",
"CAMBODIA"=>"KH",
"CAMEROON"=>"CM",
"CANADA"=>"CA",
"CAPE VERDE"=>"CV",
"CAYMAN ISLANDS"=>"KY",
"CENTRAL AFRICAN REPUBLIC"=>"CF",
"CHAD"=>"TD",
"CHILE"=>"CL",
"CHINA"=>"CN",
"CHRISTMAS ISLAND"=>"CX",
"COCOS (KEELING) ISLANDS"=>"CC",
"COLOMBIA"=>"CO",
"COMOROS"=>"KM",
"CONGO"=>"CG",
"CONGO, THE DEMOCRATIC REPUBLIC OF THE"=>"CD",
"COOK ISLANDS"=>"CK",
"COSTA RICA"=>"CR",
"CÔTE D'IVOIRE"=>"CI",
"CROATIA"=>"HR",
"CUBA"=>"CU",
"CURAÇAO"=>"CW",
"CYPRUS"=>"CY",
"CZECH REPUBLIC"=>"CZ",
"DENMARK"=>"DK",
"DJIBOUTI"=>"DJ",
"DOMINICA"=>"DM",
"DOMINICAN REPUBLIC"=>"DO",
"ECUADOR"=>"EC",
"EGYPT"=>"EG",
"EL SALVADOR"=>"SV",
"EQUATORIAL GUINEA"=>"GQ",
"ERITREA"=>"ER",
"ESTONIA"=>"EE",
"ETHIOPIA"=>"ET",
"FALKLAND ISLANDS (MALVINAS)"=>"FK",
"FAROE ISLANDS"=>"FO",
"FIJI"=>"FJ",
"FINLAND"=>"FI",
"FRANCE"=>"FR",
"FRENCH GUIANA"=>"GF",
"FRENCH POLYNESIA"=>"PF",
"FRENCH SOUTHERN TERRITORIES"=>"TF",
"GABON"=>"GA",
"GAMBIA"=>"GM",
"GEORGIA"=>"GE",
"GERMANY"=>"DE",
"GHANA"=>"GH",
"GIBRALTAR"=>"GI",
"GREECE"=>"GR",
"GREENLAND"=>"GL",
"GRENADA"=>"GD",
"GUADELOUPE"=>"GP",
"GUAM"=>"GU",
"GUATEMALA"=>"GT",
"GUERNSEY"=>"GG",
"GUINEA"=>"GN",
"GUINEA-BISSAU"=>"GW",
"GUYANA"=>"GY",
"HAITI"=>"HT",
"HEARD ISLAND AND MCDONALD ISLANDS"=>"HM",
"HOLY SEE (VATICAN CITY STATE)"=>"VA",
"HONDURAS"=>"HN",
"HONG KONG"=>"HK",
"HUNGARY"=>"HU",
"ICELAND"=>"IS",
"INDIA"=>"IN",
"INDONESIA"=>"ID",
"IRAN, ISLAMIC REPUBLIC OF"=>"IR",
"IRAQ"=>"IQ",
"IRELAND"=>"IE",
"ISLE OF MAN"=>"IM",
"ISRAEL"=>"IL",
"ITALY"=>"IT",
"JAMAICA"=>"JM",
"JAPAN"=>"JP",
"JERSEY"=>"JE",
"JORDAN"=>"JO",
"KAZAKHSTAN"=>"KZ",
"KENYA"=>"KE",
"KIRIBATI"=>"KI",
"KOREA, DEMOCRATIC PEOPLE'S REPUBLIC OF"=>"KP",
"KOREA, REPUBLIC OF"=>"KR",
"KUWAIT"=>"KW",
"KYRGYZSTAN"=>"KG",
"LAO PEOPLE'S DEMOCRATIC REPUBLIC"=>"LA",
"LATVIA"=>"LV",
"LEBANON"=>"LB",
"LESOTHO"=>"LS",
"LIBERIA"=>"LR",
"LIBYAN ARAB JAMAHIRIYA"=>"LY",
"LIECHTENSTEIN"=>"LI",
"LITHUANIA"=>"LT",
"LUXEMBOURG"=>"LU",
"MACAO"=>"MO",
"MACEDONIA, THE FORMER YUGOSLAV REPUBLIC OF"=>"MK",
"MADAGASCAR"=>"MG",
"MALAWI"=>"MW",
"MALAYSIA"=>"MY",
"MALDIVES"=>"MV",
"MALI"=>"ML",
"MALTA"=>"MT",
"MARSHALL ISLANDS"=>"MH",
"MARTINIQUE"=>"MQ",
"MAURITANIA"=>"MR",
"MAURITIUS"=>"MU",
"MAYOTTE"=>"YT",
"MEXICO"=>"MX",
"MICRONESIA, FEDERATED STATES OF"=>"FM",
"MOLDOVA, REPUBLIC OF"=>"MD",
"MONACO"=>"MC",
"MONGOLIA"=>"MN",
"MONTENEGRO"=>"ME",
"MONTSERRAT"=>"MS",
"MOROCCO"=>"MA",
"MOZAMBIQUE"=>"MZ",
"MYANMAR"=>"MM",
"NAMIBIA"=>"NA",
"NAURU"=>"NR",
"NEPAL"=>"NP",
"NETHERLANDS"=>"NL",
"NEW CALEDONIA"=>"NC",
"NEW ZEALAND"=>"NZ",
"NICARAGUA"=>"NI",
"NIGER"=>"NE",
"NIGERIA"=>"NG",
"NIUE"=>"NU",
"NORFOLK ISLAND"=>"NF",
"NORTHERN MARIANA ISLANDS"=>"MP",
"NORWAY"=>"NO",
"OMAN"=>"OM",
"PAKISTAN"=>"PK",
"PALAU"=>"PW",
"PALESTINIAN TERRITORY, OCCUPIED"=>"PS",
"PANAMA"=>"PA",
"PAPUA NEW GUINEA"=>"PG",
"PARAGUAY"=>"PY",
"PERU"=>"PE",
"PHILIPPINES"=>"PH",
"PITCAIRN"=>"PN",
"POLAND"=>"PL",
"PORTUGAL"=>"PT",
"PUERTO RICO"=>"PR",
"QATAR"=>"QA",
"RÉUNION"=>"RE",
"ROMANIA"=>"RO",
"RUSSIAN FEDERATION"=>"RU",
"RWANDA"=>"RW",
"SAINT BARTHÉLEMY"=>"BL",
"SAINT HELENA, ASCENSION AND TRISTAN DA CUNHA"=>"SH",
"SAINT KITTS AND NEVIS"=>"KN",
"SAINT LUCIA"=>"LC",
"SAINT MARTIN (FRENCH PART)"=>"MF",
"SAINT PIERRE AND MIQUELON"=>"PM",
"SAINT VINCENT AND THE GRENADINES"=>"VC",
"SAMOA"=>"WS",
"SAN MARINO"=>"SM",
"SAO TOME AND PRINCIPE"=>"ST",
"SAUDI ARABIA"=>"SA",
"SENEGAL"=>"SN",
"SERBIA"=>"RS",
"SEYCHELLES"=>"SC",
"SIERRA LEONE"=>"SL",
"SINGAPORE"=>"SG",
"SINT MAARTEN (DUTCH PART)"=>"SX",
"SLOVAKIA"=>"SK",
"SLOVENIA"=>"SI",
"SOLOMON ISLANDS"=>"SB",
"SOMALIA"=>"SO",
"SOUTH AFRICA"=>"ZA",
"SOUTH GEORGIA AND THE SOUTH SANDWICH ISLANDS"=>"GS",
"SPAIN"=>"ES",
"SRI LANKA"=>"LK",
"SUDAN"=>"SD",
"SURINAME"=>"SR",
"SVALBARD AND JAN MAYEN"=>"SJ",
"SWAZILAND"=>"SZ",
"SWEDEN"=>"SE",
"SWITZERLAND"=>"CH",
"SYRIAN ARAB REPUBLIC"=>"SY",
"TAIWAN, PROVINCE OF CHINA"=>"TW",
"TAJIKISTAN"=>"TJ",
"TANZANIA, UNITED REPUBLIC OF"=>"TZ",
"THAILAND"=>"TH",
"TIMOR-LESTE"=>"TL",
"TOGO"=>"TG",
"TOKELAU"=>"TK",
"TONGA"=>"TO",
"TRINIDAD AND TOBAGO"=>"TT",
"TUNISIA"=>"TN",
"TURKEY"=>"TR",
"TURKMENISTAN"=>"TM",
"TURKS AND CAICOS ISLANDS"=>"TC",
"TUVALU"=>"TV",
"UGANDA"=>"UG",
"UKRAINE"=>"UA",
"UNITED ARAB EMIRATES"=>"AE",
"UNITED KINGDOM"=>"GB",
"UNITED STATES"=>"US",
"UNITED STATES MINOR OUTLYING ISLANDS"=>"UM",
"URUGUAY"=>"UY",
"UZBEKISTAN"=>"UZ",
"VANUATU"=>"VU",
"VENEZUELA, BOLIVARIAN REPUBLIC OF"=>"VE",
"VIET NAM"=>"VN",
"VIRGIN ISLANDS, BRITISH"=>"VG",
"VIRGIN ISLANDS, U.S."=>"VI",
"WALLIS AND FUTUNA"=>"WF",
"WESTERN SAHARA"=>"EH",
"YEMEN"=>"YE",
"ZAMBIA"=>"ZM",
"ZIMBABWE"=>"ZW");
return $return;
}

/**
 * Calculates the offset from UTC for a given timezone
 *
 * @return integer
 */
function getTimeZoneOffset($timeZone) {
    $dateTimeZoneUTC = new DateTimeZone("UTC");
    $dateTimeZoneCurrent = new DateTimeZone($timeZone);

    $dateTimeUTC = new DateTime("now",$dateTimeZoneUTC);
    $dateTimeCurrent = new DateTime("now",$dateTimeZoneCurrent);

    $offset = (($dateTimeZoneCurrent->getOffset($dateTimeUTC))/60);
    return $offset;
}
?>


    <label for="timeZone">Timezone<br />
        <select id="timeZone" name="timeZone">
            <?php echo displayTimeZoneSelect("America/Toronto");?>
        </select>
    </label>

Answer 2

This PHP function do the Job for you an give back an array:

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;
}

This PHP function give back an array of all existing Timezones including Offset:

Use it e.g. like this:

print_r(time_zonelist());

Answer 3

For those using CodeIgniter, there's a built-in Date Helper function called timezone_menu. These:

$this->load->helper('date');
echo timezone_menu('GMT', 'form-control', 'dropdown-name', ['id' => 'ci-timezone']);

Produce the following output:

<select name="dropdown-name" class="form-control" id="ci-timezone">
  <option value="UM12">(UTC -12:00) Baker/Howland Island</option>
  <option value="UM11">(UTC -11:00) Niue</option>
  <option value="UM10">(UTC -10:00) Hawaii-Aleutian Standard Time, Cook Islands, Tahiti</option>
  <option value="UM95">(UTC -9:30) Marquesas Islands</option>
  <option value="UM9">(UTC -9:00) Alaska Standard Time, Gambier Islands</option>
  <option value="UM8">(UTC -8:00) Pacific Standard Time, Clipperton Island</option>
  <option value="UM7">(UTC -7:00) Mountain Standard Time</option>
  <option value="UM6">(UTC -6:00) Central Standard Time</option>
  <option value="UM5">(UTC -5:00) Eastern Standard Time, Western Caribbean Standard Time</option>
  <option value="UM45">(UTC -4:30) Venezuelan Standard Time</option>
  <option value="UM4">(UTC -4:00) Atlantic Standard Time, Eastern Caribbean Standard Time</option>
  <option value="UM35">(UTC -3:30) Newfoundland Standard Time</option>
  <option value="UM3">(UTC -3:00) Argentina, Brazil, French Guiana, Uruguay</option>
  <option value="UM2">(UTC -2:00) South Georgia/South Sandwich Islands</option>
  <option value="UM1">(UTC -1:00) Azores, Cape Verde Islands</option>
  <option value="UTC" selected="selected">(UTC) Greenwich Mean Time, Western European Time</option>
  <option value="UP1">(UTC +1:00) Central European Time, West Africa Time</option>
  <option value="UP2">(UTC +2:00) Central Africa Time, Eastern European Time, Kaliningrad Time</option>
  <option value="UP3">(UTC +3:00) Moscow Time, East Africa Time, Arabia Standard Time</option>
  <option value="UP35">(UTC +3:30) Iran Standard Time</option>
  <option value="UP4">(UTC +4:00) Azerbaijan Standard Time, Samara Time</option>
  <option value="UP45">(UTC +4:30) Afghanistan</option>
  <option value="UP5">(UTC +5:00) Pakistan Standard Time, Yekaterinburg Time</option>
  <option value="UP55">(UTC +5:30) Indian Standard Time, Sri Lanka Time</option>
  <option value="UP575">(UTC +5:45) Nepal Time</option>
  <option value="UP6">(UTC +6:00) Bangladesh Standard Time, Bhutan Time, Omsk Time</option>
  <option value="UP65">(UTC +6:30) Cocos Islands, Myanmar</option>
  <option value="UP7">(UTC +7:00) Krasnoyarsk Time, Cambodia, Laos, Thailand, Vietnam</option>
  <option value="UP8">(UTC +8:00) Australian Western Standard Time, Beijing Time, Irkutsk Time</option>
  <option value="UP875">(UTC +8:45) Australian Central Western Standard Time</option>
  <option value="UP9">(UTC +9:00) Japan Standard Time, Korea Standard Time, Yakutsk Time</option>
  <option value="UP95">(UTC +9:30) Australian Central Standard Time</option>
  <option value="UP10">(UTC +10:00) Australian Eastern Standard Time, Vladivostok Time</option>
  <option value="UP105">(UTC +10:30) Lord Howe Island</option>
  <option value="UP11">(UTC +11:00) Srednekolymsk Time, Solomon Islands, Vanuatu</option>
  <option value="UP115">(UTC +11:30) Norfolk Island</option>
  <option value="UP12">(UTC +12:00) Fiji, Gilbert Islands, Kamchatka Time, New Zealand Standard Time</option>
  <option value="UP1275">(UTC +12:45) Chatham Islands Standard Time</option>
  <option value="UP13">(UTC +13:00) Samoa Time Zone, Phoenix Islands Time, Tonga</option>
  <option value="UP14">(UTC +14:00) Line Islands</option>
</select>

Answer 4

Variant 1

Result:

...
[America/Scoresbysund] => (UTC+00:00) America/Scoresbysund
[Atlantic/Azores] => (UTC+00:00) Atlantic/Azores
[Atlantic/Reykjavik] => (UTC+00:00) Atlantic/Reykjavik
[Atlantic/St_Helena] => (UTC+00:00) Atlantic/St_Helena
[UTC] => (UTC+00:00) UTC
[Africa/Algiers] => (UTC+01:00) Africa/Algiers
[Africa/Bangui] => (UTC+01:00) Africa/Bangui 
...

Code:

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

$result = [];
foreach ($tzlist as $timezone) {
    $offset = (new DateTimeZone($timezone))->getOffset(new DateTime);
    $offsetPrefix = $offset < 0 ? '-' : '+';
    $offsetFormatted = gmdate('H:i', abs($offset));
    $utcOffset = "(UTC$offsetPrefix$offsetFormatted)";

    $result[$timezone] = "${$utcOffset} $timezone";
}
asort($result);
print_r($result);

Variant 2

Result:

Array
(
    [0] => Array
        (
            [value] => Africa/Abidjan
            [offset] => +00:00
            [text] => (UTC+00:00) Africa/Abidjan
        )

    [1] => Array
        (
            [value] => Africa/Conakry
            [offset] => +00:00
            [text] => (UTC+00:00) Africa/Conakry
        )
...

Code:

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

$result = [];
foreach ($tzlist as $timezone) {
    $offset = (new DateTimeZone($timezone))->getOffset(new DateTime);
    $offsetPrefix = $offset < 0 ? '-' : '+';
    $offsetFormatted = gmdate('H:i', abs($offset));
    $utcOffset = "UTC$offsetPrefix$offsetFormatted";

    $result[] = [
        'value' => $timezone,
        'offset' => "$offsetPrefix$offsetFormatted"
        // "text" => "($utcOffset) $timezone"
    ];
}
usort($result, function ($a, $b) { return strcmp($a["offset"], $b["offset"]); });
print_r($result);

Answer 5

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.