The below outputs the HTML <option>'s with all timezones specified in the $desiredRegions array.
function getAllTimeZones(){ $zoneIdentifiers = timezone_identifiers_list(); $zoneLocations = array(); foreach ($zoneIdentifiers as $zoneIdentifier) { $zone = explode('/', $zoneIdentifier); $desiredRegions = array('Africa', 'America', 'Antarctica', 'Arctic', 'Asia', 'Atlantic', 'Australia', 'Europe', 'Indian', 'Pacific' ); if (in_array($zone[0], $desiredRegions)) { if (isset($zone[1]) != '') { $area = str_replace('_', '', $zone[1]); if (!empty($zone[2])) { $area = $area . ' (' . str_replace('_', '', $zone[2]) . ')'; } $zoneLocations[$zone[0]][$zoneIdentifier] = $zone[0] . '/' . $area; } } } $selectOptions = ""; foreach($zoneLocations as $zoneRegion => $regionAreas) { foreach($regionAreas as $regionArea => $zoneLabel) { $currentTimeInZone = new DateTime("now", new DateTimeZone($regionArea)); $currentTimeDiff = $currentTimeInZone->format('P'); $selectOptions .= "<option value=\"$regionArea\">(GMT $currentTimeDiff) $zoneLabel</option>\n"; } } return $selectOptions;}echo getAllTimeZones();Output would look like:
<optgroup label="Africa"><option value="Africa/Abidjan">(GMT +00:00) Africa/Abidjan</option><option value="Africa/Accra">(GMT +00:00) Africa/Accra</option><option value="Africa/Addis_Ababa">(GMT +03:00) Africa/Addis Ababa</option>[...]</optgroup>Based on this gist.