$re = '/(America\/Adak|America\/Anchorage|America\/Anguilla|America\/Antigua|America\/Araguaina|America\/Argentina\/Buenos_Aires|America\/Argentina\/Catamarca|America\/Argentina\/Cordoba|America\/Argentina\/Jujuy|America\/Argentina\/La_Rioja|America\/Argentina\/Mendoza|America\/Argentina\/Rio_Gallegos|America\/Argentina\/Salta|America\/Argentina\/San_Juan|America\/Argentina\/San_Luis|America\/Argentina\/Tucuman|America\/Argentina\/Ushuaia|America\/Aruba|America\/Asuncion|America\/Atikokan|America\/Bahia|America\/Bahia_Banderas|America\/Barbados|America\/Belem|America\/Belize|America\/Blanc-Sablon|America\/Boa_Vista|America\/Bogota|America\/Boise|America\/Cambridge_Bay|America\/Campo_Grande|America\/Cancun|America\/Caracas|America\/Cayenne|America\/Cayman|America\/Chicago|America\/Chihuahua|America\/Ciudad_Juarez|America\/Costa_Rica|America\/Coyhaique|America\/Creston|America\/Cuiaba|America\/Curacao|America\/Danmarkshavn|America\/Dawson|America\/Dawson_Creek|America\/Denver|America\/Detroit|America\/Dominica|America\/Edmonton|America\/Eirunepe|America\/El_Salvador|America\/Fort_Nelson|America\/Fortaleza|America\/Glace_Bay|America\/Goose_Bay|America\/Grand_Turk|America\/Grenada|America\/Guadeloupe|America\/Guatemala|America\/Guayaquil|America\/Guyana|America\/Halifax|America\/Havana|America\/Hermosillo|America\/Indiana\/Indianapolis|America\/Indiana\/Knox|America\/Indiana\/Marengo|America\/Indiana\/Petersburg|America\/Indiana\/Tell_City|America\/Indiana\/Vevay|America\/Indiana\/Vincennes|America\/Indiana\/Winamac|America\/Inuvik|America\/Iqaluit|America\/Jamaica|America\/Juneau|America\/Kentucky\/Louisville|America\/Kentucky\/Monticello|America\/Kralendijk|America\/La_Paz|America\/Lima|America\/Los_Angeles|America\/Lower_Princes|America\/Maceio|America\/Managua|America\/Manaus|America\/Marigot|America\/Martinique|America\/Matamoros|America\/Mazatlan|America\/Menominee|America\/Merida|America\/Metlakatla|America\/Mexico_City|America\/Miquelon|America\/Moncton|America\/Monterrey|America\/Montevideo|America\/Montserrat|America\/Nassau|America\/New_York|America\/Nome|America\/Noronha|America\/North_Dakota\/Beulah|America\/North_Dakota\/Center|America\/North_Dakota\/New_Salem|America\/Nuuk|America\/Ojinaga|America\/Panama|America\/Paramaribo|America\/Phoenix|America\/Port-au-Prince|America\/Port_of_Spain|America\/Porto_Velho|America\/Puerto_Rico|America\/Punta_Arenas|America\/Rankin_Inlet|America\/Recife|America\/Regina|America\/Resolute|America\/Rio_Branco|America\/Santarem|America\/Santiago|America\/Santo_Domingo|America\/Sao_Paulo|America\/Scoresbysund|America\/Sitka|America\/St_Barthelemy|America\/St_Johns|America\/St_Kitts|America\/St_Lucia|America\/St_Thomas|America\/St_Vincent|America\/Swift_Current|America\/Tegucigalpa|America\/Thule|America\/Tijuana|America\/Toronto|America\/Tortola|America\/Vancouver|America\/Whitehorse|America\/Winnipeg|America\/Yakutat)/m';
$str = 'America/Adak
America/Anchorage
America/Anguilla
America/Antigua
America/Araguaina
America/Argentina/Buenos_Aires
America/Argentina/Catamarca
America/Argentina/ComodRivadavia
America/Argentina/Cordoba
America/Argentina/Jujuy
America/Argentina/La_Rioja
America/Argentina/Mendoza
America/Argentina/Rio_Gallegos
America/Argentina/Salta
America/Argentina/San_Juan
America/Argentina/San_Luis
America/Argentina/Tucuman
America/Argentina/Ushuaia
America/Aruba
America/Asuncion
America/Atikokan
America/Atka
America/Bahia
America/Bahia_Banderas
America/Barbados
America/Belem
America/Belize
America/Blanc-Sablon
America/Boa_Vista
America/Bogota
America/Boise
America/Buenos_Aires
America/Cambridge_Bay
America/Campo_Grande
America/Cancun
America/Caracas
America/Catamarca
America/Cayenne
America/Cayman
America/Chicago
America/Chihuahua
America/Ciudad_Juarez
America/Coral_Harbour
America/Cordoba
America/Costa_Rica
America/Coyhaique
America/Creston
America/Cuiaba
America/Curacao
America/Danmarkshavn
America/Dawson
America/Dawson_Creek
America/Denver
America/Detroit
America/Dominica
America/Edmonton
America/Eirunepe
America/El_Salvador
America/Ensenada
America/Fort_Nelson
America/Fort_Wayne
America/Fortaleza
America/Glace_Bay
America/Godthab
America/Goose_Bay
America/Grand_Turk
America/Grenada
America/Guadeloupe
America/Guatemala
America/Guayaquil
America/Guyana
America/Halifax
America/Havana
America/Hermosillo
America/Indiana/Indianapolis
America/Indiana/Knox
America/Indiana/Marengo
America/Indiana/Petersburg
America/Indiana/Tell_City
America/Indiana/Vevay
America/Indiana/Vincennes
America/Indiana/Winamac
America/Indianapolis
America/Inuvik
America/Iqaluit
America/Jamaica
America/Jujuy
America/Juneau
America/Kentucky/Louisville
America/Kentucky/Monticello
America/Knox_IN
America/Kralendijk
America/La_Paz
America/Lima
America/Los_Angeles
America/Louisville
America/Lower_Princes
America/Maceio
America/Managua
America/Manaus
America/Marigot
America/Martinique
America/Matamoros
America/Mazatlan
America/Mendoza
America/Menominee
America/Merida
America/Metlakatla
America/Mexico_City
America/Miquelon
America/Moncton
America/Monterrey
America/Montevideo
America/Montreal
America/Montserrat
America/Nassau
America/New_York
America/Nipigon
America/Nome
America/Noronha
America/North_Dakota/Beulah
America/North_Dakota/Center
America/North_Dakota/New_Salem
America/Nuuk
America/Ojinaga
America/Panama
America/Pangnirtung
America/Paramaribo
America/Phoenix
America/Port-au-Prince
America/Port_of_Spain
America/Porto_Acre
America/Porto_Velho
America/Puerto_Rico
America/Punta_Arenas
America/Rainy_River
America/Rankin_Inlet
America/Recife
America/Regina
America/Resolute
America/Rio_Branco
America/Rosario
America/Santa_Isabel
America/Santarem
America/Santiago
America/Santo_Domingo
America/Sao_Paulo
America/Scoresbysund
America/Shiprock
America/Sitka
America/St_Barthelemy
America/St_Johns
America/St_Kitts
America/St_Lucia
America/St_Thomas
America/St_Vincent
America/Swift_Current
America/Tegucigalpa
America/Thule
America/Thunder_Bay
America/Tijuana
America/Toronto
America/Tortola
America/Vancouver
America/Virgin
America/Whitehorse
America/Winnipeg
America/Yakutat
America/Yellowknife
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php