Added missing countries to the existing answers
$country_timezone = array(
'Asia/Kabul' => 'Afghanistan',
'Europe/Tirane' => 'Albania',
'Africa/Algiers' => 'Algeria',
'Pacific/Pago_Pago' => 'American Samoa',
'Europe/Andorra' => 'Andorra',
'Africa/Luanda' => 'Angola',
'America/Anguilla' => 'Anguilla',
'Antarctica/Casey' => 'Antarctica',
'Antarctica/Davis' => 'Antarctica',
'Antarctica/DumontDUrville' => 'Antarctica',
'Antarctica/Mawson' => 'Antarctica',
'Antarctica/McMurdo' => 'Antarctica',
'Antarctica/Palmer' => 'Antarctica',
'Antarctica/Rothera' => 'Antarctica',
'Antarctica/Syowa' => 'Antarctica',
'Antarctica/Troll' => 'Antarctica',
'Antarctica/Vostok' => 'Antarctica',
'America/Antigua' => 'Antigua and Barbuda',
'America/Argentina/Buenos_Aires' => 'Argentina',
'America/Argentina/Catamarca' => 'Argentina',
'America/Argentina/Cordoba' => 'Argentina',
'America/Argentina/Jujuy' => 'Argentina',
'America/Argentina/La_Rioja' => 'Argentina',
'America/Argentina/Mendoza' => 'Argentina',
'America/Argentina/Rio_Gallegos' => 'Argentina',
'America/Argentina/Salta' => 'Argentina',
'America/Argentina/San_Juan' => 'Argentina',
'America/Argentina/San_Luis' => 'Argentina',
'America/Argentina/Tucuman' => 'Argentina',
'America/Argentina/Ushuaia' => 'Argentina',
'Asia/Yerevan' => 'Armenia',
'America/Aruba' => 'Aruba',
'Antarctica/Macquarie' => 'Australia',
'Australia/Adelaide' => 'Australia',
'Australia/Brisbane' => 'Australia',
'Australia/Broken_Hill' => 'Australia',
'Australia/Darwin' => 'Australia',
'Australia/Eucla' => 'Australia',
'Australia/Hobart' => 'Australia',
'Australia/Lindeman' => 'Australia',
'Australia/Lord_Howe' => 'Australia',
'Australia/Melbourne' => 'Australia',
'Australia/Perth' => 'Australia',
'Australia/Sydney' => 'Australia',
'Europe/Vienna' => 'Austria',
'Asia/Baku' => 'Azerbaijan',
'America/Nassau' => 'Bahamas',
'Asia/Bahrain' => 'Bahrain',
'Asia/Dhaka' => 'Bangladesh',
'America/Barbados' => 'Barbados',
'Europe/Minsk' => 'Belarus',
'Europe/Brussels' => 'Belgium',
'America/Belize' => 'Belize',
'Africa/Porto-Novo' => 'Benin',
'Atlantic/Bermuda' => 'Bermuda',
'Asia/Thimphu' => 'Bhutan',
'Plurinational State of' => 'Bolivia',
'Sint Eustatius and Saba' => 'Bonaire',
'Europe/Sarajevo' => 'Bosnia and Herzegovina',
'Africa/Gaborone' => 'Botswana',
'America/Araguaina' => 'Brazil',
'America/Bahia' => 'Brazil',
'America/Belem' => 'Brazil',
'America/Boa_Vista' => 'Brazil',
'America/Campo_Grande' => 'Brazil',
'America/Cuiaba' => 'Brazil',
'America/Eirunepe' => 'Brazil',
'America/Fortaleza' => 'Brazil',
'America/Maceio' => 'Brazil',
'America/Manaus' => 'Brazil',
'America/Noronha' => 'Brazil',
'America/Porto_Velho' => 'Brazil',
'America/Recife' => 'Brazil',
'America/Rio_Branco' => 'Brazil',
'America/Santarem' => 'Brazil',
'America/Sao_Paulo' => 'Brazil',
'Indian/Chagos' => 'British Indian Ocean Territory',
'Asia/Brunei' => 'Brunei Darussalam',
'Europe/Sofia' => 'Bulgaria',
'Africa/Ouagadougou' => 'Burkina Faso',
'Africa/Bujumbura' => 'Burundi',
'Asia/Phnom_Penh' => 'Cambodia',
'Africa/Douala' => 'Cameroon',
'America/Atikokan' => 'Canada',
'America/Blanc-Sablon' => 'Canada',
'America/Cambridge_Bay' => 'Canada',
'America/Creston' => 'Canada',
'America/Dawson' => 'Canada',
'America/Dawson_Creek' => 'Canada',
'America/Edmonton' => 'Canada',
'America/Fort_Nelson' => 'Canada',
'America/Glace_Bay' => 'Canada',
'America/Goose_Bay' => 'Canada',
'America/Halifax' => 'Canada',
'America/Inuvik' => 'Canada',
'America/Iqaluit' => 'Canada',
'America/Moncton' => 'Canada',
'America/Nipigon' => 'Canada',
'America/Pangnirtung' => 'Canada',
'America/Rainy_River' => 'Canada',
'America/Rankin_Inlet' => 'Canada',
'America/Regina' => 'Canada',
'America/Resolute' => 'Canada',
'America/St_Johns' => 'Canada',
'America/Swift_Current' => 'Canada',
'America/Thunder_Bay' => 'Canada',
'America/Toronto' => 'Canada',
'America/Vancouver' => 'Canada',
'America/Whitehorse' => 'Canada',
'America/Winnipeg' => 'Canada',
'America/Yellowknife' => 'Canada',
'Atlantic/Cape_Verde' => 'Cape Verde',
'America/Cayman' => 'Cayman Islands',
'Africa/Bangui' => 'Central African Republic',
'Africa/Ndjamena' => 'Chad',
'America/Punta_Arenas' => 'Chile',
'America/Santiago' => 'Chile',
'Pacific/Easter' => 'Chile',
'Asia/Shanghai' => 'China',
'Asia/Urumqi' => 'China',
'Indian/Christmas' => 'Christmas Island',
'Indian/Cocos' => 'Cocos (Keeling) Islands',
'America/Bogota' => 'Colombia',
'Indian/Comoro' => 'Comoros',
'Pacific/Rarotonga' => 'Cook Islands',
'America/Costa_Rica' => 'Costa Rica',
'Europe/Zagreb' => 'Croatia',
'America/Havana' => 'Cuba',
'America/Curacao' => 'Curaçao',
'Asia/Famagusta' => 'Cyprus',
'Asia/Nicosia' => 'Cyprus',
'Europe/Prague' => 'Czech Republic',
'Africa/Abidjan' => 'Côte d Ivoire',
'Europe/Copenhagen' => 'Denmark',
'Africa/Djibouti' => 'Djibouti',
'America/Dominica' => 'Dominica',
'America/Santo_Domingo' => 'Dominican Republic',
'America/Guayaquil' => 'Ecuador',
'Pacific/Galapagos' => 'Ecuador',
'Africa/Cairo' => 'Egypt',
'America/El_Salvador' => 'El Salvador',
'Africa/Malabo' => 'Equatorial Guinea',
'Africa/Asmara' => 'Eritrea',
'Europe/Tallinn' => 'Estonia',
'Africa/Addis_Ababa' => 'Ethiopia',
'Atlantic/Stanley' => 'Falkland Islands (Malvinas)',
'Atlantic/Faroe' => 'Faroe Islands',
'Pacific/Fiji' => 'Fiji',
'Europe/Helsinki' => 'Finland',
'Europe/Paris' => 'France',
'America/Cayenne' => 'French Guiana',
'Pacific/Gambier' => 'French Polynesia',
'Pacific/Marquesas' => 'French Polynesia',
'Pacific/Tahiti' => 'French Polynesia',
'Indian/Kerguelen' => 'French Southern Territories',
'Africa/Libreville' => 'Gabon',
'Africa/Banjul' => 'Gambia',
'Asia/Tbilisi' => 'Georgia',
'Europe/Berlin' => 'Germany',
'Europe/Busingen' => 'Germany',
'Africa/Accra' => 'Ghana',
'Europe/Gibraltar' => 'Gibraltar',
'Europe/Athens' => 'Greece',
'America/Danmarkshavn' => 'Greenland',
'America/Nuuk' => 'Greenland',
'America/Scoresbysund' => 'Greenland',
'America/Thule' => 'Greenland',
'America/Grenada' => 'Grenada',
'America/Guadeloupe' => 'Guadeloupe',
'Pacific/Guam' => 'Guam',
'America/Guatemala' => 'Guatemala',
'Europe/Guernsey' => 'Guernsey',
'Africa/Conakry' => 'Guinea',
'Africa/Bissau' => 'Guinea-Bissau',
'America/Guyana' => 'Guyana',
'America/Port-au-Prince' => 'Haiti',
'Europe/Vatican' => 'Holy See (Vatican City State)',
'America/Tegucigalpa' => 'Honduras',
'Asia/Hong_Kong' => 'Hong Kong',
'Europe/Budapest' => 'Hungary',
'Atlantic/Reykjavik' => 'Iceland',
'Asia/Kolkata' => 'India',
'Asia/Jakarta' => 'Indonesia',
'Asia/Jayapura' => 'Indonesia',
'Asia/Makassar' => 'Indonesia',
'Asia/Pontianak' => 'Indonesia',
'Islamic Republic of' => 'Iran',
'Asia/Baghdad' => 'Iraq',
'Europe/Dublin' => 'Ireland',
'Europe/Isle_of_Man' => 'Isle of Man',
'Asia/Jerusalem' => 'Israel',
'Europe/Rome' => 'Italy',
'America/Jamaica' => 'Jamaica',
'Asia/Tokyo' => 'Japan',
'Europe/Jersey' => 'Jersey',
'Asia/Amman' => 'Jordan',
'Asia/Almaty' => 'Kazakhstan',
'Asia/Aqtau' => 'Kazakhstan',
'Asia/Aqtobe' => 'Kazakhstan',
'Asia/Atyrau' => 'Kazakhstan',
'Asia/Oral' => 'Kazakhstan',
'Asia/Qostanay' => 'Kazakhstan',
'Asia/Qyzylorda' => 'Kazakhstan',
'Africa/Nairobi' => 'Kenya',
'Pacific/Kanton' => 'Kiribati',
'Pacific/Kiritimati' => 'Kiribati',
'Pacific/Tarawa' => 'Kiribati',
'Democratic Peoples Republic of' => 'Korea',
'Asia/Kuwait' => 'Kuwait',
'Asia/Bishkek' => 'Kyrgyzstan',
'Asia/Vientiane' => 'Lao Peoples Democratic Republic',
'Europe/Riga' => 'Latvia',
'Asia/Beirut' => 'Lebanon',
'Africa/Maseru' => 'Lesotho',
'Africa/Monrovia' => 'Liberia',
'Africa/Tripoli' => 'Libya',
'Europe/Vaduz' => 'Liechtenstein',
'Europe/Vilnius' => 'Lithuania',
'Europe/Luxembourg' => 'Luxembourg',
'Asia/Macau' => 'Macao',
'the Former Yugoslav Republic of' => 'Macedonia',
'Indian/Antananarivo' => 'Madagascar',
'Africa/Blantyre' => 'Malawi',
'Asia/Kuala_Lumpur' => 'Malaysia',
'Asia/Kuching' => 'Malaysia',
'Indian/Maldives' => 'Maldives',
'Africa/Bamako' => 'Mali',
'Europe/Malta' => 'Malta',
'Pacific/Kwajalein' => 'Marshall Islands',
'Pacific/Majuro' => 'Marshall Islands',
'America/Martinique' => 'Martinique',
'Africa/Nouakchott' => 'Mauritania',
'Indian/Mauritius' => 'Mauritius',
'Indian/Mayotte' => 'Mayotte',
'America/Bahia_Banderas' => 'Mexico',
'America/Cancun' => 'Mexico',
'America/Chihuahua' => 'Mexico',
'America/Hermosillo' => 'Mexico',
'America/Matamoros' => 'Mexico',
'America/Mazatlan' => 'Mexico',
'America/Merida' => 'Mexico',
'America/Mexico_City' => 'Mexico',
'America/Monterrey' => 'Mexico',
'America/Ojinaga' => 'Mexico',
'America/Tijuana' => 'Mexico',
'Europe/Monaco' => 'Monaco',
'Asia/Choibalsan' => 'Mongolia',
'Asia/Hovd' => 'Mongolia',
'Asia/Ulaanbaatar' => 'Mongolia',
'Europe/Podgorica' => 'Montenegro',
'America/Montserrat' => 'Montserrat',
'Africa/Casablanca' => 'Morocco',
'Africa/Maputo' => 'Mozambique',
'Asia/Yangon' => 'Myanmar',
'Africa/Windhoek' => 'Namibia',
'Pacific/Nauru' => 'Nauru',
'Asia/Kathmandu' => 'Nepal',
'Europe/Amsterdam' => 'Netherlands',
'Pacific/Noumea' => 'New Caledonia',
'Pacific/Auckland' => 'New Zealand',
'Pacific/Chatham' => 'New Zealand',
'America/Managua' => 'Nicaragua',
'Africa/Niamey' => 'Niger',
'Africa/Lagos' => 'Nigeria',
'Pacific/Niue' => 'Niue',
'Pacific/Norfolk' => 'Norfolk Island',
'Pacific/Saipan' => 'Northern Mariana Islands',
'Europe/Oslo' => 'Norway',
'Asia/Muscat' => 'Oman',
'Asia/Karachi' => 'Pakistan',
'Pacific/Palau' => 'Palau',
'America/Panama' => 'Panama',
'Pacific/Bougainville' => 'Papua New Guinea',
'Pacific/Port_Moresby' => 'Papua New Guinea',
'America/Asuncion' => 'Paraguay',
'America/Lima' => 'Peru',
'Asia/Manila' => 'Philippines',
'Pacific/Pitcairn' => 'Pitcairn',
'Europe/Warsaw' => 'Poland',
'Atlantic/Azores' => 'Portugal',
'Atlantic/Madeira' => 'Portugal',
'Europe/Lisbon' => 'Portugal',
'America/Puerto_Rico' => 'Puerto Rico',
'Asia/Qatar' => 'Qatar',
'Europe/Bucharest' => 'Romania',
'Asia/Anadyr' => 'Russian Federation',
'Asia/Barnaul' => 'Russian Federation',
'Asia/Chita' => 'Russian Federation',
'Asia/Irkutsk' => 'Russian Federation',
'Asia/Kamchatka' => 'Russian Federation',
'Asia/Khandyga' => 'Russian Federation',
'Asia/Krasnoyarsk' => 'Russian Federation',
'Asia/Magadan' => 'Russian Federation',
'Asia/Novokuznetsk' => 'Russian Federation',
'Asia/Novosibirsk' => 'Russian Federation',
'Asia/Omsk' => 'Russian Federation',
'Asia/Sakhalin' => 'Russian Federation',
'Asia/Srednekolymsk' => 'Russian Federation',
'Asia/Tomsk' => 'Russian Federation',
'Asia/Ust-Nera' => 'Russian Federation',
'Asia/Vladivostok' => 'Russian Federation',
'Asia/Yakutsk' => 'Russian Federation',
'Asia/Yekaterinburg' => 'Russian Federation',
'Europe/Astrakhan' => 'Russian Federation',
'Europe/Kaliningrad' => 'Russian Federation',
'Europe/Kirov' => 'Russian Federation',
'Europe/Moscow' => 'Russian Federation',
'Europe/Samara' => 'Russian Federation',
'Europe/Saratov' => 'Russian Federation',
'Europe/Ulyanovsk' => 'Russian Federation',
'Europe/Volgograd' => 'Russian Federation',
'Africa/Kigali' => 'Rwanda',
'Indian/Reunion' => 'Réunion',
'America/St_Barthelemy' => 'Saint Barthélemy',
'Ascension and Tristan da Cunha' => 'Saint Helena',
'America/St_Kitts' => 'Saint Kitts and Nevis',
'America/St_Lucia' => 'Saint Lucia',
'America/Marigot' => 'Saint Martin (French part)',
'America/Miquelon' => 'Saint Pierre and Miquelon',
'America/St_Vincent' => 'Saint Vincent and the Grenadines',
'Pacific/Apia' => 'Samoa',
'Europe/San_Marino' => 'San Marino',
'Africa/Sao_Tome' => 'Sao Tome and Principe',
'Asia/Riyadh' => 'Saudi Arabia',
'Africa/Dakar' => 'Senegal',
'Europe/Belgrade' => 'Serbia',
'Indian/Mahe' => 'Seychelles',
'Africa/Freetown' => 'Sierra Leone',
'Asia/Singapore' => 'Singapore',
'America/Lower_Princes' => 'Sint Maarten (Dutch part)',
'Europe/Bratislava' => 'Slovakia',
'Europe/Ljubljana' => 'Slovenia',
'Pacific/Guadalcanal' => 'Solomon Islands',
'Africa/Mogadishu' => 'Somalia',
'Africa/Johannesburg' => 'South Africa',
'Atlantic/South_Georgia' => 'South Georgia and the South Sandwich Islands',
'Africa/Juba' => 'South Sudan',
'Africa/Ceuta' => 'Spain',
'Atlantic/Canary' => 'Spain',
'Europe/Madrid' => 'Spain',
'Asia/Colombo' => 'Sri Lanka',
'Africa/Khartoum' => 'Sudan',
'America/Paramaribo' => 'Suriname',
'Arctic/Longyearbyen' => 'Svalbard and Jan Mayen',
'Africa/Mbabane' => 'Swaziland',
'Europe/Stockholm' => 'Sweden',
'Europe/Zurich' => 'Switzerland',
'Asia/Damascus' => 'Syrian Arab Republic',
'Province of China' => 'Taiwan',
'Asia/Dushanbe' => 'Tajikistan',
'United Republic of' => 'Tanzania',
'Asia/Bangkok' => 'Thailand',
'Asia/Dili' => 'Timor-Leste',
'Africa/Lome' => 'Togo',
'Pacific/Fakaofo' => 'Tokelau',
'Pacific/Tongatapu' => 'Tonga',
'America/Port_of_Spain' => 'Trinidad and Tobago',
'Africa/Tunis' => 'Tunisia',
'Europe/Istanbul' => 'Turkey',
'Asia/Ashgabat' => 'Turkmenistan',
'America/Grand_Turk' => 'Turks and Caicos Islands',
'Pacific/Funafuti' => 'Tuvalu',
'Africa/Kampala' => 'Uganda',
'Europe/Kiev' => 'Ukraine',
'Europe/Simferopol' => 'Ukraine',
'Europe/Uzhgorod' => 'Ukraine',
'Europe/Zaporozhye' => 'Ukraine',
'Asia/Dubai' => 'United Arab Emirates',
'Europe/London' => 'United Kingdom',
'America/Adak' => 'United States',
'America/Anchorage' => 'United States',
'America/Boise' => 'United States',
'America/Chicago' => 'United States',
'America/Denver' => 'United States',
'America/Detroit' => 'United States',
'America/Indiana/Indianapolis' => 'United States',
'America/Indiana/Knox' => 'United States',
'America/Indiana/Marengo' => 'United States',
'America/Indiana/Petersburg' => 'United States',
'America/Indiana/Tell_City' => 'United States',
'America/Indiana/Vevay' => 'United States',
'America/Indiana/Vincennes' => 'United States',
'America/Indiana/Winamac' => 'United States',
'America/Juneau' => 'United States',
'America/Kentucky/Louisville' => 'United States',
'America/Kentucky/Monticello' => 'United States',
'America/Los_Angeles' => 'United States',
'America/Menominee' => 'United States',
'America/Metlakatla' => 'United States',
'America/New_York' => 'United States',
'America/Nome' => 'United States',
'America/North_Dakota/Beulah' => 'United States',
'America/North_Dakota/Center' => 'United States',
'America/North_Dakota/New_Salem' => 'United States',
'America/Phoenix' => 'United States',
'America/Sitka' => 'United States',
'America/Yakutat' => 'United States',
'Pacific/Honolulu' => 'United States',
'Pacific/Midway' => 'United States Minor Outlying Islands',
'Pacific/Wake' => 'United States Minor Outlying Islands',
'America/Montevideo' => 'Uruguay',
'Asia/Samarkand' => 'Uzbekistan',
'Asia/Tashkent' => 'Uzbekistan',
'Pacific/Efate' => 'Vanuatu',
'Bolivarian Republic of' => 'Venezuela',
'Asia/Ho_Chi_Minh' => 'Viet Nam',
'British' => 'Virgin Islands',
'U.S.' => 'Virgin Islands',
'Pacific/Wallis' => 'Wallis and Futuna',
'Africa/El_Aaiun' => 'Western Sahara',
'Asia/Aden' => 'Yemen',
'Africa/Lusaka' => 'Zambia',
'Africa/Harare' => 'Zimbabwe',
'Europe/Mariehamn' => 'Åland Islands'
);
Ref: https://timezonedb.com/time-zones
