Generating a List of Timezones with PHP

I often find myself developing applications that need to support users in different timezones, it is important to these users that dates are displayed in their preferred timezone. I thought I would share with you the function I use to create a list of timezones, each with their current UTC offset.

The following function will return a list of timezones ordered by their UTC offset and timezone identifier in ascending order.

/**
 * Return an array of timezones
 * 
 * @return array
 */
function timezoneList()
{
    $timezoneIdentifiers = DateTimeZone::listIdentifiers();
    $utcTime = new DateTime('now', new DateTimeZone('UTC'));

    $tempTimezones = array();
    foreach ($timezoneIdentifiers as $timezoneIdentifier) {
        $currentTimezone = new DateTimeZone($timezoneIdentifier);

        $tempTimezones[] = array(
            'offset' => (int)$currentTimezone->getOffset($utcTime),
            'identifier' => $timezoneIdentifier
        );
    }

    // Sort the array by offset,identifier ascending
    usort($tempTimezones, function($a, $b) {
		return ($a['offset'] == $b['offset'])
			? strcmp($a['identifier'], $b['identifier'])
			: $a['offset'] - $b['offset'];
    });

	$timezoneList = array();
    foreach ($tempTimezones as $tz) {
		$sign = ($tz['offset'] > 0) ? '+' : '-';
		$offset = gmdate('H:i', abs($tz['offset']));
        $timezoneList[$tz['identifier']] = '(UTC ' . $sign . $offset . ') ' .
			$tz['identifier'];
    }

    return $timezoneList;
}

/**

* Return an array of timezones

* @return array

function timezoneList()

{

$timezoneIdentifiers = DateTimeZone::listIdentifiers();

$utcTime = new DateTime('now', new DateTimeZone('UTC'));

$tempTimezones = array();

foreach ($timezoneIdentifiers as $timezoneIdentifier) {

$currentTimezone = new DateTimeZone($timezoneIdentifier);

$tempTimezones[] = array(

'offset' => (int)$currentTimezone->getOffset($utcTime),

'identifier' => $timezoneIdentifier

);

}

// Sort the array by offset,identifier ascending

usort($tempTimezones, function($a, $b) {

return ($a['offset'] == $b['offset'])

? strcmp($a['identifier'], $b['identifier'])

: $a['offset'] - $b['offset'];

});

$timezoneList = array();

foreach ($tempTimezones as $tz) {

$sign = ($tz['offset'] > 0) ? '+' : '-';

$offset = gmdate('H:i', abs($tz['offset']));

$timezoneList[$tz['identifier']] = '(UTC ' . $sign . $offset . ') ' .

$tz['identifier'];

}

return $timezoneList;

}

Here is the format of the array which this function returns:

Array
(
    [Pacific/Midway] => (UTC -11:00) Pacific/Midway
    [Pacific/Niue] => (UTC -11:00) Pacific/Niue
    [Pacific/Pago_Pago] => (UTC -11:00) Pacific/Pago_Pago
    ...
    [Pacific/Enderbury] => (UTC +13:00) Pacific/Enderbury
    [Pacific/Tongatapu] => (UTC +13:00) Pacific/Tongatapu
    [Pacific/Kiritimati] => (UTC +14:00) Pacific/Kiritimati
)

Array

(

[Pacific/Midway] => (UTC -11:00) Pacific/Midway

[Pacific/Niue] => (UTC -11:00) Pacific/Niue

[Pacific/Pago_Pago] => (UTC -11:00) Pacific/Pago_Pago

...

[Pacific/Enderbury] => (UTC +13:00) Pacific/Enderbury

[Pacific/Tongatapu] => (UTC +13:00) Pacific/Tongatapu

[Pacific/Kiritimati] => (UTC +14:00) Pacific/Kiritimati

)

You could for example use this to generate an HTML drop down select of timezones using the following code:

$timezoneList = timezoneList();
echo '<select name="timezone">';
foreach ($timezoneList as $value => $label) {
    echo '<option value="' . $value . '">' . $label . '</option>';
}
echo '</select>';

$timezoneList = timezoneList();

echo '<select name="timezone">';

foreach ($timezoneList as $value => $label) {

echo '<option value="' . $value . '">' . $label . '</option>';

}

echo '</select>';

I hope this comes in handy!

David Hancock

Web & Mobile Application Developer

Generating a List of Timezones with PHP